clamp for mechanical pencil + stick eraser

I use this because good mechanical pencils (like ones with retracting pocket safe tips and auto lead rotation clutches) have overly optimistic tiny erasers which are next to useless. So far this clamp holds them solidly and isn't awkward to write with, if held in the right way.

Uses these products:

Uni Mechanical Pencil Kurutoga Pipe Slide Model 0.5mm
Pentel ZE21BP3K6 Clic Eraser

http://a.co/0bkRPcd
http://a.co/7UlK7HE

The outer barrel diameters of the pencil and stick eraser hold