While you CAN paint hair with the mouse... It's a pain in the --- to get looking reasonably "not painted" results.

Try ebay - and yeah, the first reccomendation would be Wacom, but I had an Aiptek 6x8 that was great. Yeah, takes an AA batt for the pen - it didn't suck THAT bad for me, but it was a little weird to have it die on me in the middle of drawing.

And BTW - if/when you DO get a tablet, expect the first few weeks to be odd for you as you learn to use it instead of a mouse - and then once you get past that you'll NEVER go back when it comes to drawing.

Good luck-
-Lew ;-)