I use a Logitech BRIO attached to a flexible webcam stand.

You don't need something as expensive as a BRIO (I had the cam already for working at home) if you are only using it for Spelltable. Just make sure whatever camera you get is compatible for the mount you have. I really like the flexible arms, but they aren't terribly steady. They are normally fine, but if you already have a desk that moves a little, then it might be an issue.

Another note, you want your play area to be bright, but you don't want the light shining directly down on your table. So I'd avoid cameras with built in lights, as those tend to cause glare on the card sleeves (in my personal experience at least).