Depends where you are but look in your yellow pages for "HEATING REPLACEMENT PARTS AND CONTROLS".
They are a national company and should be able to tell you if the parts are available.
Some suppliers are now not selling specific gas parts to non corgi customers but they should still be able to give you info.
I recently got a part for a b/gas customer when they told him the same and they eventually came back and fixed it...
Good luck
T.h.s
May 2007