You won't be able to (almost certainly) for 2 reasons:
1. It isn't like a standard fan. It has a different connector to your video card PCB, it will be connected differently, and the radius will potentially be specific to the card. If you can find an old card with a similar sized fan with the same mounting system and the same header (unlikely) it may work, but then it would either have the same noise levels, or worse performance.
2. It is low profile, so you won't be able to get an after market heatsink.
Your best bet is to take off the shroud from the graphics card, buy a decent 80mm fan or two, buy some cable ties and ghetto mod it onto the heatsink with the cable ties. The only downside to that is not all, or even most, of the air will be exhausted, so you will need fairly good ventalation inside your case to get rid of that hot air.
Newegg.com - SILVERSTONE SCOOL81 80mm Case Fan
Newegg.com - Scythe S-FLEX SFF80C 80mm Case Fan
Newegg.com - GELID Solutions FN-PX08-20 80mm Case Fan with Intelligent PWM control
any of those would do, but I personally would go with a Scythe fan or two. They will plug into your motherboard if you have a free fan header, so then you can use a program like Speedfan to change the fan speed to make it as quiet as possible whilst keeping the temps as low as possible