Can you list the value in Ω (ohms) and power rating of the Pot you're looking for? (ie: 1M log/audio, rated at 1W)
If I were a betting man, I would guess you're looking for a replacement volume pot? I'd be willing to go a little bit further and guess that the repair shop you brought it to today supplied you with the manufacturer's parts list for the amplifier on your way out, so you could purchase the accurate part as well?
If you can provide that information too, that would help us better help you.