I purchased the heatsink from Moderator 007, think I got the last one he made. You could do the same thing with one from H22A over at CPF.
You have to cut the tower off the original switch to make room for the heatsink. Once that and the wiring were done I filed the sinkpad down below the size of the hole in the rebel reflector. I mounted the sink so the reflector just bottoms against it when the head is screwed down all the way.
All assembled just unscrew the head to the proper height for focus.
A few photos here.