You'll soon determine if belt sander takes it off quick enough. Maybe grinder is a better choice !!
Agreed. Sockets are made of some seriously tough steel. They'll grind ok on a zirconia or ceramic belt if that's what you've got, but will chew up aluminum oxide pretty quickly. They'll also eat up grinding wheels, but it's not like you have a lot of metal to remove anyway, so modifying just one should be a simple enough task. Just keep it turning slowly (to make the cut evenly around the circumference) and keep it cool.
If you have a lathe with a toolpost grinder, that's a great option, but maybe I'm asking too much. I will say that turning a chromed socket with HSS and even cobalt cutters is an exercise in frustration (voice of experience here).
HF is a potential source for a cheap socket, but so is Sears (Craftsman), HD (Husky), or Lowes (Kobalt). Heck, if you're only buying ONE socket, even a SnapOn isn't going to hurt your wallet.
Just find a place that sells open stock individual sockets.
On that note, I've picked up individual sockets at flea markets when I've had these sort of projects. There'll often be a bin full of sockets on sale for pennies a piece. I'll grab some USA made common sizes, and I keep a drawer of misfit tools around just for this sort of emergency modification.