Will upload pics of finished part when I get it.
Step 1: Materials
An airsoft gun (as a reference for sizing)
A micrometer or ruler, depends how precise you want to be.
3D Design software. I used Autodesk Inventor (free student version) but there are free alternatives like Google sketch up or Blender.
Access to a 3D printer (or free instructables print) or cnc if you can.
A flashlight also for sizing reference.
4 bolts and nuts (small)