Was able to purchase the fan from http://allpartsmac.com/

Make sure to remove old adhesive tape from both the iMac *and* the screen before putting new adhesive tape on.

- Consider carefully vacuuming the dust out of the fan base before installing the new fan.

- Make extra sure not to drop the T10 screws into the iMac when you put them back.

- Make sure to remove the adhesive tape from both the iMac and the screen before putting new adhesive tape on.

- You'll need to reset PRAM when you turn the iMac back on.