The link on the main reprap forum page http://reprap.org/wiki/Prusa_i3_Build_Manual clearly point to https://github.com/alexrj/Prusa3/tree/i3-unterwelt for MGS plastic parts.
This is in error!
It should be https://github.com/Joaz/machine_parts/tree/master/mgs_prusa
This also has the source and is for 30mm holes, perfect for I3
I have updated the link on the wiki
I now need to reprint...