I Added a parametric new model to fit all your clamping needs!

Find the parametric model in my library or here: LINK

Just a generic pole mount for umbrellas/poles/antennas etc.

Scale the model to fit your need. :)
Currently fits a 37mm pole very snug. 

Mounts with two screws, and clamps the pole.
 
For outdoor use please use ABS or similar outdoor proof material.