I bought a couple of tubes and a few extra companion boards on FT months ago. Just checked, the ones I got are discontinued but there might be another brand with spare boards available, probably on FT.Where are these replacement boards sold?
Followup on the pre-coiled wire I got from FT. They seem to be the resistance advertised. I can make my own coils but it's nice to have the option. They all cost 5 cents a coil or less.