I would suggest a Harmony remote. It's a universal remote but not like the ones you used to buy that sucked - you can program them. The Harmony One is probably your best bet but you can get cheaper ones and some even bigger more expensive ones. Kalahari seems to have some very good prices on them.
It (WDTV) also now supports bluetooth keyboards (with a dongle) and Logitech used to have a very nice palm size keyboard. Much better than thir onscreen keyboard!