Pumped out a few buttons for you or anyone else that needs them. They're at ShareCG, at the moment:

http://www.sharecg.com/v/79150/browse/5/3D-Model/Very-Basic-Buttons

I'll also upload them here, for funsies.

.obj format, includes a low-res button for Poser low-res, distance renders that uses Poser's default smooth-shading to render a fairly circular button with very low geometry. The rest are made of moderate, but still fairly low, geometry, suitable for mucking about with as base objects for clothing buttons. Each has two material zones, front and back, if anyone cares about that sort of thing. UV Maps included, for what it's worth. All quads, IIRC, in case anyone's software has to have them.

Enjoy!

(If you ever need anything specific or of better quality, let me know. If I have time, I don't mind making it as a freebie.)