I got a PC about five years ago that shipped with an Arctic Freezer 64 CPUD heatsink and fan. The other day the fan became dislodged and one of the fins snapped off.

My mobo is an A8n-SLI and I am using an AMD processor - the heatsink therefore utilizes a mounting bracket for socket 939.

Not onlyhas the fan got a snapped fin, but the one of the fiddly little mounting nipples on the heatsink to which the fan attaches also sheared off.

So, I need help finding a CPU heatsink and fan that matches the following criteria
- compatible with socket 939 processor
- mounts on the exisiting bracket (I really do not want to have to take out the mobo)
- has similar dimensions to the Arctic 64 (roughly 10cm by 11 cm by 12.5cm) so that it doesn't interfere with the memory sockets.

Can anyone assist please?

http://www.arctic.ac/en/p/cooling/cpu.html

Alpine 64 Pro or Freezer 7 Pro v2

Hi, you could just get another Freezer 7 or the new v2 version. Personally I’ve been looking at the Freezer 13 which is similar size but with 4 heatpipes and more cooling capacity. Might be deeper... check ram clearance.
Also the Cooler Master Hyper TX3 definitely worth a look, small slim tower with reasonable PWM fan that spins down to ~900rpm. (Your board only has 3pin CPU header but does have fan control that should work, fairly well anyway) The TX3 just clips on to the socket and can be mounted in both orientations, it tends to be very cheap to buy too 
Xigmatech also do similar sized direct touch heatpipe cooler with similar cooling abilities. S963 or SD963 I think.

Regards, Seb

I've got an original Freezer 64 that I pulled out of a 939/Athlon box I just dismantled. It's six years old and a little dusty, but ran fine. I don't need to make money on it, just happy to send it to someone who will use it. $5 plus shipping from Massachusetts, USA, and it's yours, as is. Probably wouldn't make sense if you're not in the States. Let me know if you're interested.