This is what I ordered that worked:

[Pack of 2] Panasonic CR2354 3V Lithium Cell Blister Packaging Battery https://smile.amazon.com/dp/B00KFSX8KQ/ref=cm_sw_r_cp_api_fabt1_BQiVFb6CAD9NJ?_encoding=UTF8&psc=1

I ordered another brand on Amazon that wouldn’t fit, didn’t have the right side profile...Amazon took them back no issue, so given the battery is not super common just order and hope you get good ones?

As for a legit non Amazon source? Try these, have ordered plenty of electronics from they they are reputable companies. Downside is shipping will make them expensive unless you need to refill you electronic components supplies too:

https://www.mouser.com/ProductDetail/Panasonic-Battery/CR2354?qs=1eQvB6Dk1vibW%252Bpa2OEGKA%3D%3D

https://www.digikey.com/en/products/detail/panasonic-bsg/CR2354/107120