I got myself a Kensington Webracer (touchpad + some extra buttons, nice for controlling MP3-player apps). Still trying to make all additional buttons work with WinXP though.
As far as I know, Kensington still produces some very nice looking & working devices, although they may be a little bit overpriced. Anyways, you get 1st class quality.
I recommend looking for touchpads on Ebay. I got mine there as well. And I would look in every computer-store nearby as well. I have seen a few touchpads in stores near my hometown.
[Edit: Well, thanks to another thread in this forum I got it to work now]