I had the same issue with the oven and I bought the part (it is a mercury filled and not a thermocouple) which I replaced and it worked fine... for a while. Unfortunately, I waited too long between buying the part and installing it, and I am afraid it became damaged or I damaged it during installation because it stopped working after a few uses. I bought the part in Martinique at a local chandlery and I don't remember its name.
If you find a supplier, I would be happy to chip in to buy one part like yours and one extra for the oven. The replacement for the oven was complicated as it required almost full disassembly but for the burners, I think it can be easily done in place. Feel free to come by Ipanema next Thurs evening or, if we have gone to Gloucester, on Sunday evening. Even better, it would be great if you join us in Gloucester.