Perhaps you could slather them with release agent then lay up new fiberglass ones using those as the mold. The fiberglass ones will be a little larger so it may be an issue with the fit. You could then use the one you laid up as the "mold" and lay up on the inside of the new one to get an exact size replacement. Personally my solenoid valve corroded and it was time for new hoses, and regulator, etc. So I scrapped the whole mess and the stove and installed an origo stove/oven to run off alcohol. Very happy with the replacement.