is wireless a must? not a lot of options there unfortunately, if so.
but if not, you have the Logitech G100s (it is a Logitech indeed, but a bit better one, and affordable/cheap) which is small, good omron microswitches, very light weight (can even be modded to weigh even less, there is a metal disk inside of it) and 500-1000-2000 DPI options.
then there's the Zowie FK1, a bit larger but still considered small. very nice microswitches as well, huano I think, a bit harder to press but otherwise really solid buttons. 400-800-1600-3200 dpi options, no drivers needed.
also quite light. good shape and scroll wheel is decent on it.
roccat kone pure military - not really recommended if you want something less fussy. the drivers are not the greatest and it looks a bit 'gaming'-y. can handle 50-5000 dpi in 50dpi increments.
light weight, small, great button switches, awesome scroll wheel. bit more ergonomic than the fk1/g100s mentioned above.
even if the drivers are annoying, you only need to set it up once then you can uninstall it, since it saves the settings onto the onboard memory.
mionix avior 7000 - perhaps a bit bigger, but good buttons and great scroll wheel, and sort of lightweight. I used it with fingertip grip as well and it was nice. 50-5000 dpi in 50dpi increments, same sensor hardware as the kone pure military. perhaps a bit wide in the butt for fingertip grip for smaller hands though.
if those are too advanced, perhaps a budget would be good to know