I see lots of these on Ebay, a few on Amazon, and they're relatively inexpensive. Industrial distributors want a lot of $$$. Looking for something that will read into the 1200 degC range, and thermocouples that will last more than a couple of cycles. What I've read leads me to K-type thermocouples. Thoughts? Insights?

There are none. I've searched, I've asked. That is, you have to work with 500" C max with those hand gun temp meters,

Blacksmiths building gas forges often use a k-type thermocouple and a digital display.

I don't have brand or sources to recommend, but if you go googling in THAT context, you're likely to find more results than rocket-related.