I use a Wacom Graphire4 which I believe has recently been superseded by the Wacom Bamboo. They make a huge difference to mapping and I couldn't do my maps without it. It cost me £80 but a quick hunt on ebay will find lots that are cheaper.

I'd stick with Wacom, having had a nisis before. You pay more, but it is worth it. Also, don't worry about going small. I use an A6 drawing area and it is quite enough. It also fits in my laptop case.