Summary

This is remix of MarkBenson's spool mount. I modified plate/frame mount to accommodate thinner (3mm) steel frame (like one sold by Replikeo) and also made mount longer with holes at the bottom to secure it with screws.

Instructions

Print two frame holders/mounts (frame_holder) and two spool holders (Spool_spindle_holder). Cut 2 identical length M6 or 1/4" threaded rods and fit to each, with nuts and bolts, a plate mount and a spool mount. Cut a length of M8 or 5/16" threaded rod to carry your filament spool (with optional universal spool adapters http://www.shapedo.com/wildseyed/osfa_filament_spool_holder) and press fit it into the spool mounts.
Optionally secure frame mounts with a screw and nut on the bottom (4/40 of about 18mm lengh screws work)

Prusa i3 Spool Mount for 3mm Frame