Any OLD applaince repairmen out there?

[C-5 CC]

We have a 1948 or 49 Kelvinator Stove. I know, I know...get rid of it and get a new one..blah..blah..blah. Anyway, this is a great old stove, but we have had trouble lately w/ the oven. We will set it for 350, push in the preheat button, and when it pops out, put the stuff in the oven...walk away...come back in twenty minutes and the temp has fallen to 200-250 and wont raise back up, no matter what we set it at.
The local applaince guy says we are screwed...no parts available anywhere. Kelvinator was sold off many years ago.
Do any of you know of any locations that we might be able to get parts from. The local guy says it sounds like a bad thermostat. Any info would be appreciated.
Brandon