Look for switches like these at Newark/Farnell/Element14, RS, whomever your favorite supplier is. Connect up the Common and NC (normally closed) contacts. Read their data sheet to see what temperature they are rated for.
200C or 200F? 200C is pretty darn hot! That's solder reflow temperature
You know the basics - spring to hold two contacts together, mechanical housing to hold them and let something external push them apart. Coil springs can also lose springiness at elevated temperatures - so you've got a good mechanical challenge on your hands.