K8n neo4 fan sounds aweful

I'm super un-happy. I have a system with a athlon 64 x2, RAID, 4 gig of memory - all nice stuff. In it is a K8N Neo4 V2.0 motherboard. I just had to replace the power supply in it, and the CPU fan.

Right next to the PCIe slot (there is only 1) is a little fan - I'm assuming thats the northbridge fan? Anyway, it spins like crazy, sounds like a lawnmower, and then slows down and gets hot. I'm afraid its going to melt. If I push on the fan a little, it sounds better (I can't stand there all day!).

So, I need a replacement fan. Thing is - its right next to the video card. Does anyone know if there is a factory replacement for that, or is there a fan thats super low profile that will fit? I'd hate to spend 25$ on a fan, just to have it not fit.

THANKS