WB21X5208
It looks like the GE part number is stamped on the back of your old thermostat - WB21X5208. Appears there are some on eBay but pricey. I believe an older part number may have been WB21X177.
You could also do some research to see what a compatible aftermarket one from Robertshaw or somewhere else would substitute to and do a search for one of those.
Make sure you keep that ring thats on the front face of the old one - its an adapter that is often needed on these old GE stoves to fasten a newer thermostat to the control panel.