A friend asked me to modify the Makerbot Filament Spool holder ( thingiverse.com/thing:7105 ) to work with the Heavy Duty Printable Filament Holder clip ( thingiverse.com/thing:10219 ). I didn't have the appropriate version of SolidWorks, so I had to rebuild it from scratch, but that was simple enough. It rotates pretty well on the clip, and it's pretty simple to swap out spools if you have more than one.