I designed this Airbrush handle specifically custom fit for the Iwata Eclipse HP-CS airbrush. There's some other handles out there, but they don't print well and/or don't fit my brush. So I set out to design something that printed well, with minimal supports, and fits perfectly.

Printing:
Body: Set on its bottom, so the circle hole for the airbrush body is vertical. The clampy part should be on the print surface. No supports needed.

Handle: Set it on its right side (left if you're left-handed) so the smoother side will be in your palm. You'll probably want supports on the slot, I'd recommend painting them on instead of letting them get placed automatically. I printed one without supports and it was honestly fine, and if you glue it in place it won't matter how it looks.

Glue the handle into the body after printing if you'd like it to stay in place.

The fusion 360 file is included and is parameterized to some extent. You can adjust the points in the first sketch to change the handle curvature if the one I used isn't right for you. Change the Taper in the parameters to make it thicker/thinner. 5mm was too thin, 10mm worked better for me. It's not perfectly 1:1 because of the chamfering and curvature.

You can also adjust tolerance. I used .15mm because that's what works best for my printer. Adjust for yours if needed.