Mountain Biking - Rear derailleur

I apologize if you discuss this all the time. I searched but didn't find the answer to the question I have.

I have a Giant Cadex 2 mountain bike. It's old. It came out in about 1992. It had Sun Tour components on it and they worked beautifully.

Then a few weeks ago something happened as I was pedalling and I managed to snap the part of the RD that hangs down (with the little wheel on it) in two.

I know next to nothing about mountain bike components. Does anyone have any suggestions for what level derailleur I ought to get to more or less match the old Sun Tour. This has become the bike I use to ride around town and run errands on. I don't want to call it a beater because it's carbon, and too nice for that, but i won't be riding it hard on trails and the like.

Thanks for your patience.

Did you break your derailleur hanger?, I guess you could get yourself a new Suntour derailleur if you like or you can get a new one, from SRAM or Shimano, just visit your nearest dealer and get his opinion, there are some riders whom are willing to give you their opinions. Im leaving this out because Im only 2 years old when you bought your Mountain Bike

Priceless. Simply priceless.

Does SunTour deraillures use the same gearing as Shimano?

sorry, Im not sure

If the bike has indexed shifters (Accushift), you'll need a Suntour derailleur from the same era to work perfectly. I see them on eBay all the time. A modern Shimano would probably work almost right.
What model Suntour derailleur is the one you broke?
Can you post a picture?