No one sells compact PWM fan controllers.

[Meaker]

PWM mate - discontinued
Micro PWM DIY project - discontinued

At this rate I may buy an old zalman extreme to get one

 

[Meaker]

Phanteks produce one for their cases, but I think it can be purchased separately.

Fan Hub but not controller.

tealc on here has a lot of experience with them IIRC.

Looks fairly trivial to DIY.

Not to make it look decent and I only want to make one, the time involved in designing, soldering etc I am better off just buying a zalman cooler and taking it off.