Hubsan X4 Prop Guard
Prop guard for Hubsan X4 H107C (motor diameter 8,5 mm)
These guards give enough protection to absorb slight bumps into walls, but if you crash hard enough they won't help much. They weigh less than the original guard though.
The fit around the motors is a bit tight so you may need to file or sand them out a little bit. This will also depend on your printer.
There are two versions, one with a ceiling guard and one without.
The version without ceiling guard weighs about 0,43 grams each, the one with ceiling guard weighs about 0,48 grams. You need 4, so that makes 1,72 or 1,92 grams total.
Update 4 jan 2015: Added a sturdier version of the guard with ceiling protector. This one has little ribs added to the ceiling protector and the guard and 'eye' parts are a little bit thicker. Weight has increased to 0,56 gram. This one should be a little bit more crash proof.
Update 5 feb 2015: Added a version for the non-camera hubsan with 7 mm motors. The holes are exactly 7 mm, so you might need to use a 7 mm drill bit to make them fit if you printer is not precise enough. This is the sturdier version with ceiling guards.