You can buy Ubigi eSIMs in the US or anywhere...I've done it several times. I just bought two 500 MB day passes on Ubigi in the US because I ran out of data on Verizon.

Also not sure what you mean about not being able to buy a Ubigi plan multiple times. I've done it several times...

Sounds like Stork is a little cheaper than Ubigi, which is nice. One thing I noticed about Ubigi is it seems to route all my data through France (even though I was roaming on T-mobile US) so latency was pretty high. One thing that sounds better about Ubigi is that their app works well and shows you how much data you have left.

Oh, if you have Verizon you can still make/receive calls on your Verizon account and send/receive SMS if you download the Verizon Message+ app. It basically lets you access all the "telephone" aspects of your account via a data connection.