Side spool holder for Reprap Prism

After printing (and using) the useful "standalone" spool holder (http://www.thingiverse.com/thing:32204) for my RepRap Prism 1.5 (made at the CCSTI FabLab in Grenoble), I was looking for something that could be attached directly at the side of the printer but I didn't find exactly what I want, so I decided to derive it from what looks to be closest to the design I dreamed of