How to find replacement fan for PSU?

Solution 1:

Buy a standard 12cm case fan. The mounting holes on 12cm case fans are 105mm apart, which is exactly what you measured. You might want to check if the replacement fan is not thicker than the original (or it might not fit in the PSU), but most likely it won't be a problem. PSU fans are the same as regular case (chassis) fans.

As for the electrical connection, the extra one or two wires are for speed control (PWM speed set and feedback). If you leave these disconnected, the fan will just work at max RPM. Given that the original fan only had two wires, this seems to be the design intent of the manufacturer of the device. Just leave the extra wires disconnected (or cut them off), and it'll work fine.

If you want a silent option, you want to look at case fans advertised with low dB values. Specific recommendations are out of scope on this site, but there are hundreds of tech review websites which can recommend particular models.