OpenSCAD code included for modifications. Just print on your favorite open source 3D printer and clean up. You can use a pretty low infill for this kind of a part.
You'll need 3-M3 Nuts and a Low profile M3x20/25mm Screw. You need 2 of the 3 M3 nuts for the thumb screw. If you look at the Lens holder thumbscrew, it will be put together in the same way, except instead of the head of the screw, it will be a nut.
The mount slides onto the OpenBeam as seen in the pictures. You secure it in place with a combination of m3s and our optical thumb screw. Then mount optical components using 8mm diameter smooth rod.
You can get OpenBeam at http://www.openbeamusa.com/Extrusions/
More information see this
This component is part of the Open-source Optics Library: Zhang C, Anzalone NC, Faria RP, Pearce JM (2013) Open-Source 3D-Printable Optics Equipment. PLoS ONE 8(3): e59840.
This is part of a larger project to reduce the cost of scientific equipment using open-source hardware. Read more here
Thanks to Nick for the OpenSCAD code and Terence Tam for Open Beam.