My first choice, the Zigzagoon, has a problem: the actual plushie's foot is maybe a bit too small for the Qi charging coil. So I searched for other Pokemon plushies that:

1. have a wide base, and
2. have appendages that can be moved a bit with servo motors.

Turns out, these are pretty hard to find, especially in a plushie. But I found that the Slugma (Pokedex) meets both criteria. It has a nice big foot and a head and some dripping fire that can be wiggled. So I ordered a plushie, which arrived today. It's much smaller than the Zigzagoon, but it's a very simple shape to work with: