A4 Tech - Battery Free Wireless Optical Mouse
They have several models - mine is the NB-90
& it's just brilliant.
It comes with a special mouse pad that powers the mouse so the mouse itself is cable & battery free
& it has 6 different buttons & two wheels that you can program/set up to work the way you want it to.
I love it - it works better than any other wireless mouse I've ever used, (& that's despite being dropped on many occasions & having coffee spilled on the mouse pad several hundred times )
AND it only cost about £12 (plus it saves me spending a fortune on batteries)