Can you buy iPhone 5s sims on their own without buying the device?

Can you buy iPhone 5s sims on their own without buying the device?

Yes - from anywhere that sells the device

There's no such thing as an "iPhone 5s SIM".

It's just a regular nanoSIM which virtually all phone shops should have in stock as there are a number of phones now using SIMs of that particular form factor.

Not all phone service providers offer nanoSIMs yet though, so if yours doesn't offer them either switch provider or use a special tool to cut a regular microSIM or miniSIM down to size.

You mean the nanoSIM?

Yea. Any carrier that offers them.