While I have heavily used Wacom tablets, they're pricey if a newer model and a pain to update and keep in shape, and often have fatal design flaws that cause them to cease functioning after a certain period of time. However, they are incredibly easy to use, if you're willing to put up with the frustration of software errors and updates from time to time. I am currently using an older model, an Intuos 3D (CTH-690), which is medium sized and very very portable (as it's thinner than its Pro cousins). As for cheapness, I'm unaware of its current price other than it is cheaper than Pro.
I also wouldn't suggest Pros, as the smaller model has a fatal design flaw that causes them to cease function within 4 years.