The Spektrum Dx9 transmitter has trim switches with unnecessarily flimsy actuator arms -- see the attached photo. My brother broke two and was ready to send it in for repairs for (?? $$) or buy a new transmitter. I said "Hold up"... why do you think I have a 3D printer?

Designed in OpenSCAD, it's way more solid than the original.

Print it standing on the pivot point, with supports "touching buildplate", and recommend 100% infill. It may take just a touch of sanding or filing to adjust the actuating points to trip the switches, but not much.

I don't know which transmitter model other than the Dx9 the part fits, but if yours looks like the photo of the OEM part, this should do the trick.