I remixed the original file to accommodate M3 screws rather than M2.5, and I also made the extension taller. I am currently using this on my Printrbot Plus 1404 for any interested.

06/03/15:
There are now 4 versions of this adapter to fit varying uses. I have added a version which has a slimmer notch for mounting which is more similar to the Printrbot Hotend. I also added two variants that have M3 nuts on the backside to reduce the likelihood of the two halves coming apart.