Lysol sells a small battery powered soap dispenser. They're $15 or so, but I find they go on clearance for about $7.
I have 2, I like them, so does my young son. The thing is the refills are expensive.
Fortunately you can just pop off the top and fill with normal liquid soap. Saves a lot of money, and you don't have to use their scented soaps, some of them are quite strong.