Here's an Amazon link for the LE! https://www.amazon.com/Overlord-II-Season-Two-Blu-ray/dp/B07J33SJ57
They don't charge at all until it ships and even though it's using the base price instead of the discounted one like Funimation is, they always lower it later on!
Every single one was purchased from Amazon. They are the limited edition releases of each.
Season One is actually labeled as the complete series, and the hardest one to find from what I can gather. I bought it awhile back when it was on sale for around $60 before tax.
Season 2 and 3 are currently available on Amazon right now with Prime shipping. Season 2 looks to have just had a price drop as well which would be a good time to get it. You just have to be sure you click the secondary option of limited edition. It should show the boxes accordingly.
Edit I found links to seasons 2 & 3