Reply to Pitch Wheels

I am building a DIY controller and am believeing of including a pitch wheel, like those on synths and keyboard controllers. I know that these are spring-loaded potentiometers of some kind, but I don't know the technical name of them. I googled around and haven't been able to figure it out. I'd love to be able to just order one somewhere, or am I gonna have to buy a cheap old synth or controller simply for the part. Thanks.