I found that my extruder stepper was running hot (even after tuning the current) on 15-30hr prints and I was getting print failures due to the printed drive gear on the Pitan extruder softening and spinning on the D shaft.
I found ScottW1's design to be elegant and sufficiently low-profile to clear the gantry shoulder, but I wanted to add a 4040 fan.
This design assumes that you will be using a thermal pad between the heatsink and stepper and may not work correctly without one as it does not provide much clamping pressure on the heatsink.
The heatsink this is designed for is 40x40x11
Edit: I added a version that holds the heatsink a little bit tighter to the stepper.
whatever PETG or ABS
Print it circle side down. I have not had any issues with the legs breaking due to the layer orientation.
I extracted the basic dimensions of the clip from ScottW1's design and re-drafted it in Fusion360 and added holes for the 4040 fan.