Small wireless controller?

So, I've got two daughters. Ages 3 and 4(she'll be 5 in 9 days). I'm trying to introduce them into the PC Master Race (kidding, just trying to get them into gaming). Last Christmas I bought them each a mini controller, Power A Pro EX Mini. Even though the controllers are much smaller, they're still not quite the right fit for their hands, but close enough. Especially for the oldest.

However, as you guessed by the title, the wires are really annoying.

Does anyone make a decent "mini" wireless controller for PC? I'm not having much luck finding anything that fits the bill. 

Well there is a gamepad from SteelSeries but it is a little pricey: LINK

Here is a video showing the size of compared to a Nexus 7 Tablet

I know that it runs through bluetooth but I have no idea if it is able to run through the wired USB, there is some software that you can install on to remap the controller for games as well. 

www.youtube.com/watch?v=sZTht185TzE

Thanks for the link. The price is a little steep, but it is what I'm after..and there doesn't seem to many other choices. Plus my motherboard has a Bluetooth module - so I'm good to go!