This is my version of the bumper. The original holds the board in what I think odd and unpractical places and the clips where causing problems when printing (stringing causing problems).But I liked the basic design. I redesigned it from scratch to the dimensions of my Arduino Uno rev 2 (I think). The board is being held in place exactly on the four corners so it can't go anywhere. The clips are made stronger and because of the way it is designed it is easier to clean up after printing and stringing doesn't affect the critical design of the clip.
Downside of this design, It fits only original Arduino's. These arduino's have slightly rounded corners. Older Arduino's and some knock-offs don't have the rounded corners and therefor the holder won't fit.

Should fit:

• Arduino Uno
• Arduino Leonardo
• *Arduino YUN
• Arduino Zero
• *Arduino M0 Pro
• *Adafruit Metro
• needs to be confirmed.

02/05/2014 UPDATE:
New version (V2.0) available for download. The bumper has been made a bit more beefy. Makes it easier to print and can withstand some more abuse.

04/05/2014 Update:
What's even better then printing one bumper, printing four in one go! I have added an .stl that will let you print four bumpers in one session.

If you print this, please click the "I made one" on this thingiverse page.