Not strictly a derivative, but serves a similar purpose.

I need a thing that can hold onto a bushing on one side, and perpendicular to that, can hold onto a rod of a specified size.

The default sizes for this thing is 5/16" on one side, and 11mm on the other. The bushing I am using has an inner diameter of 1/4", and outer diameter of 5/16". On the perpendicular, I'm inserting a carbon fiber rod that has an outer diameter of roughly 11mm. That rod can be friction fit, or glued, or whatever, depending on what you're doing.

1) Figure out where you might be able to use a perpendicular fitting for round rods.
2) Print one of these out
3) Slip a bushing into the side that goes all the way through
4) Slip a matching smooth steel rod into the bushing to form an axle
5) Slip your stationary rod in the perpendicular hole
6) Rejoice!