I've been annoyed by the few VTX antenna mounts you can find online that fit the standoff width of the Martian IV 5" quad frame, they all break off quite easy. So I made my own.
I've used Tinkercad for this design as the geometry is quite simple.
It features holes letting zip ties go through for swallow-style RX antenna mounting.
Get it on Thingiverse: https://www.thingiverse.com/thing:4164768