https://www.amazon.com/gp/product/B078LSVVTB/
I have this saved in case i ever lose mine, check the reviews a couple say it works perfectly with the index.
ifixit didn't sell it back when I lost mine. I found the one I'm linking through reddit I think. I have it set on 12v and haven't had any issues in the year and a half I've had it.
How about something like this along with a power supply. Each fan should draw a max of around 120mA and this unit provides 500mA, or 4 fans worth.
Edit#?: This might help too. It should save you from having to splice any wires.