I've looked all around for something like this, and decided i'd take a crack at putting it together with openSCAD using the original Prusa design files by Joseph Prusa ( https://github.com/prusajr/PrusaMendel ), as well as LM8UU Snap Fit Bearing Holder by Jolijar ( http://www.thingiverse.com/thing:7755 )this should provide enough space to fit two lm8uu bearings with a bit of a gap in between.this is my first time using openSCAD, so i can only hope this works and helps someone!Note: the STL files were compiled for a Metric prusa