I'm not sure on that, never seen one but that doesn't mean it does not exist.
 
As far as getting it done, not sure how the cards fan controller will do with a fan not made for it. Might spin too fast or too slow, could require more amps than the controller can handle and burn it out.
 
If your motherboard has an option for fan control you could use that, play around with the different settings and find one that works under load and still stays cool/quite, whatever your preference.

You could get a cable like this: http://www.moddiy.com/products/Mini-4%252dPin-GPU-to-2-x-4%252dPin-PWM-Fan-Adapter.html
But a 3-Pin fan will run on full speed all the time.
Maybe consider attaching it to the mainboard and controlling the fan with "Speedfan".