Some different sized bag clips. I wanted the sturdiness of http://www.thingiverse.com/thing:5627 and the one piece hinge of http://www.thingiverse.com/thing:2868 so I redesigned with the best aspects of both. I also removed the sharp edges so it is comfortable to apply pressure to it.

UPDATE: Use v2 files

I've provided four sizes, 60mm, 80mm, 100mm and 120mm. The pictures show all but the 100mm. I printed in ABS with 3 walls and 10% infill and they seem the perfect balance between strength and flex.

Thanks to the others for inspiration. Please improve on my design and post a derivative!

UPDATE: 18th Sep 2012, I've added new versions (v2) that have an improved larger clip. I recommend using those instead of the originals.