Modification of up2it's Bukobot filament spool holder (http://www.thingiverse.com/thing:153465) to fit the MM2's frame. This version is trimmed to print faster, with a larger hole at the top for different sized rods (up to diameter of 12.8mm).
Print 2, grab a rod and throw your filament spool on it, attach rod through top row, mount on top of your MM2!
25% infill should be fine
This has only been tested on standard spools (1kg). A spool with a larger diameter may not work.