Modified Broomstick threaded end. I designed this for a larger pole (22.3 mm) and with a thicker base so that it can take a little more force

The center hole also has a conical interior so that the part can be printed without support material.

Edit it here if you need to make more customizations: https://www.tinkercad.com/things/0ggiZg0Z7JY

The original posting of this design was really thin near the connection to the threads. The current design is greatly improved. Sorry about that.