I got a new on/off switch for my Jet lathe via David Biven (Biven Machinery Sales) although when I took the old one off and cleared it of dust, it started working again !
Depending on your needs, you might find a Triton superjaw works for you. It's the only modern portable solution I've found of an acceptable quality and stability. You can use the vice element to hold a small workbench type top using a batten glued and screwed to the underside. Not overly...