I'm having the same problem, but worse, with the same card. Mine idles at about 70C and Ive caught it as high as 110C
when gaming in a 1280x768 window on my 24" display, even with the fan manually set to 100% of speed.
I've reseated the current fan/heatsink and used new thermal compound, to no avail. The fan sound is loud and warbles, making me think the bearings are shot.
Did you ever find a replacement fan/heat sink?