What you want is possible with a service like Knowroaming (https://www.knowroaming.com/product/travel-sim-card/), you just have to add funds every 9 months. But it is impractical because the per unit costs (voice, SMS, MB) are ridiculously high.
SIM cards are cheap. You can buy a Tracfone SIM card for $1 or less at Target, Best Buy, or Amazon (https://www.amazon.com/dp/B072FTW1MB) and the SIM cards will work on any Tracfone brand, Page Plus would be the most practical for a one month visit, provided that their phones support Verizon.
You can buy a cheap Page Plus compatible phone (any Total Wireless phone) from Target or Walmart (or from HSN with a year of service included, see https://www.hsn.com/shop/samsung-cell-phones/ec0373-1043-6664-10962).
You can also use the HSN Tracfone phones on other Tracfone Verizon brands (Page Plus, Total Wireless).
I haven't had any foreign visitors for a while, due to Covid, but I used to do the same thing, activate a phone for them to use while they were here (I certainly have plenty of spare phones!).
Not fantastic, since these are $1 add-ons and you have to pay for a plan, but maybe good if you happen to be there anyway?
For all of these: Promotion valid ONLY on SIM Cards shipped from and sold by Amazon. Purchase date of SIM must have started on 3/1/19 to Qualify.
TracFone: https://www.amazon.com/Tracfone-Keep-Your-Phone-Prepaid/dp/B0728N8PT9
Get a $25 Amazon eGift Card when you buy a Tracfone Sim Kit and activate a new line of service by 4/30/2019 on the Tracfone website. Minimum $15 plan required with service charge and applicable sales tax due at sale. eGift Card sent within 7-14 days of activation. While supplies last.
Total Wireless: https://www.amazon.com/Total-Wireless-Keep-Phone-Prepaid/dp/B072FTW1MB
PROMOTION: Get a $25 Amazon eGift Card when you buy a Total Wireless Sim Kit and activate a new line of service by 4/30/2019 on the Total Wireless website.Single Line $25/$35 plan required with service charge and applicable sales tax due at sale. Multi Line Airtime Plan does not Apply. eGift Card sent within 7-14 days of activation. While supplies last.
Simple Mobile: https://www.amazon.com/Total-Wireless-Keep-Phone-Prepaid/dp/B072FTW1MB
PROMOTION: Get a $25 Amazon eGift Card when you buy a Simple Mobile Sim Kit and activate a new line of service by 4/30/2019 on the Simple Mobile website. Minimum $25 plan required with service charge and applicable sales tax due at sale. eGift Card sent within 7-14 days of activation. While supplies last.
Net10: https://www.amazon.com/Net10-Keep-Your-Phone-Prepaid/dp/B071FM63JT
PROMOTION: Get a $25 Amazon eGift Card when you buy a Net10 Sim Kit and activate a new line of service by 4/30/2019 on the Net10 website. Minimum $20 plan required with service charge and applicable sales tax due at sale. eGift Card sent within 7-14 days of activation. While supplies last.
For Amazon Deal, need to buy SIM from Amazon
More info at http://https://amazonsimrewards.com/
For eBay Deal, need to buy from eBay
More info at http://ebaysimrewards.com
There is a slight money maker chance if you want to try out Net10, cause SIM is $1 and minimum first month payment is $20, I don't know how much it will cost overall after taxes, but maybe like $1~4 Money Maker lol
Step 1: Purchase a SIM KIT & qualifying service plan anytime from 2/27/2020 through 4/30/2020. SIM KIT must be sold & shipped by Amazon or the tracfonewireless eBay store.
Step 2: Activate your service by 4/30/2020. You will automatically received a text message within 10 business days of activation. The text message will include a unique redemption code and instructions on how to redeem your Gift Card.
Step 3: Redeem your unique code with the instructions from the text message you receive. Please note that the unique code sent via text message can only be redeemed once and cannot be replaced. Limit of 1 Gift Card per qualifying phone number permitted.
For all of these: Promotion valid ONLY on SIM Cards shipped from and sold by Amazon or the tracfonewireless eBay store. Purchase date of SIM must have started on 2/27/2020 to Qualify.
Tracfone:
Amazon
https://www.amazon.com/dp/B0728N8PT9
eBay
https://www.ebay.com/itm/283230124002
Get a $25 eGift Card when you purchase a Tracfone Sim Kit and activate a new line of service by 4/30/2020 on the Tracfone website. Min. $19.99 plan required with service charge and applicable sales tax due at sale.
Total Wireless:
Amazon
https://www.amazon.com/dp/B072FTW1MB
eBay
https://www.ebay.com/itm/283230148008
Get a $25 eGift Card when you purchase a Total Wireless Sim Kit and activate a new line of service by 4/30/2020 on the Total Wireless website. Min. $25 plan required with service charge and applicable sales tax due at sale.
Simple Mobile:
Amazon
https://www.amazon.com/dp/B072M18F3H
eBay
https://www.ebay.com/itm/283230138604
Get a $25 eGift Card when you purchase a Simple Mobile Sim Kit and activate a new line of service by 4/30/2020 on the Simple Mobile website. Min. $25 plan required with service charge and applicable sales tax due at sale.
Net10:
Amazon
https://www.amazon.com/dp/B071FM63JT
eBay
https://www.ebay.com/itm/283230133796
Get a $25 eGift Card when you purchase a Net10 Sim Kit and activate a new line of service by 4/30/2020 on the Net10 website. Min. $20 plan required with service charge and applicable sales tax due at sale.
Still available online from Amazon for 98 cents... and they arrive in a day or two
https://www.amazon.com/eGift-Promotion-Total-Wireless-Prepaid/dp/B072FTW1MB/
Probably also available online from Walmart, Target, and Bestbuy. Tracfone (parent of Total) has a tight relationship with Walmart and has Walmart exclusive brands (Straighttalk and Walmart Family Mobile) so it is understandable that they got Walmart to pull the products with the old branding, but BestBuy and Target may still have some in the stores.