I live in London and have seen them at SHOWCASE. It's a store that sells stuff that advertised on info commercials. There's one in every large mall here in London so I'm thinking they may be in other cities as well. I think they are about $10.
I saw this small handheld one while browsing on The Source (formerly Radio Shack). It's a lot smaller than the ones at Disney but it seems like it might easily fit into a pocket or purse. I don't have one so I'm not sure how well it works.