Every now and again along comes a gadget that makes you think 'what a great idea'. This is one such, from Product-Reviews.Net, a solar powered wireless computer mouse.
However, most computer mice are in heaviest use during the daytime, and it does need direct sunlight to gain sufficient charge; so perhaps the only solution might be to buy two and alternate their use, using mouse 1 whilst mouse 2 is on charge on the windowsill? (Clever bit of marketing or what?)
Don't leave it charging while the cat's about though!