Here is what Atari originally used:
Ohmite # RES-100 Power Wirewound Rheostat, 100 ohms (the volume control)
CW Industries # GF-624-6014 Slide Switch, S.P.D.T. (the test switch)
Both of these are available at mouser.com as the part numbers 629-GF6246014 (50 cents) and 588-RES-100 ($22.59)