I have used the same approach as Grim. For static parts and parts that see little to no stress; I use PLA. For functional parts I use PETG. PETG has a better chemical resistance than PLA. I also find that PETG has a better elasticity (maintain its original shape after being compressed or stretched). think of boom tube collars or mechanical clamping type parts.
TPU is more of a rubbery type of material that usually rates around the 90's on the durometer scale. Grim suggested TPU specifically for the RX mount because of it's isolation capabilities. My suggestion would be to make a tray like you've done out of a rigid type material (PLA, PETG, or ABS). Then make an "insert" out of TPU that would provide the isolation properties for the RX.
I have never printed in TPU.