Any US carrier, in my experience.

https://www.flyamz.com/storage/2020/03/USA-SIM-Card-New-ATT-...

https://images5.tanganetwork.com/prod?bucket=tanga-fetched-i...

https://m.media-amazon.com/images/I/61bYyPhpYoL._AC_SL1200_....

All the sims I have ever received(US) come as a credit card sized item(looks like a smart card) and you break out the size you need. (sim, mini sim, micro sim)

TIL the 1FF size for SIMs (see image at https://mobile.twitter.com/phone_museum/status/1287310071907...). Thanks!

Here in UK you get that from most carriers.