you know what am I doing for my new water cooling?? Maybe you can get an idea from it
I found an old Hand Dryer. It has a blower inside
I opened it, removed the timer and the heaters and tryed it out. It blew the hell out of me with it's incredible air flow, but it makes some kind of high frequency noise. But I also found a way to control it. In my father's garage I found a fan speed controller, those that usually you find hanging on the walls that control the speed of the roof fans, with 5 speed. On just the smallest, i think it would be enough to cool a radiator and at that speed it is extreemly quite.
The only problem i encountered till now it this, i have to redo the outside shaping to make it fit the radiator, and it is quite difficicult. I still don't know if i will choose to bend some metal sheet or instead some cardboard or something soft.