If you are handy with electronics or at least have used a soldering iron, you might consider trying to de-solder and replace the triac itself. Look at the number on the triac and type it into the NTE cross reference and they will likely have an equivalent triac for a reasonable price.

Here is the link to NTE Electronics:

www.nteinc.com/...

EDIT:

While they don't offer a direct cross reference, if you can figure out the triac specifications, you could also check Mouser, Allied, or some other supplier, they almost always beat NTE's prices. Also if you use NTE's cross reference search, Allied Electronics(www.alliedelec.com/...) is an NTE distributor.