Having been in the situation a while back where I had a dead fan and couldn't afford a new card or find a suitable fan in my box of bits, with a bit of bodging, I stuck a case fan on to the heatsink with cable ties round the PCB and powered it off a spare molex, worked fine for 18 months when I replaced it, main drawback was it covered up 3 slots on the mobo with the fan stuck on it and it was a bit noisy! but it worked. Another dodge I've used in the past was again using a case fan. Use double sided sticky pads and stick on top of the adjacent slot so it blows directly at the heatsink, just needs watching to make sure it don't fall off! Super glue is better if you have no use for the slot.