DIY Recirculating Water bowl

After hearing the Cat meow for the 100th time it was brought up that he might like water that is flowing, so I decided to see what was available online and also how much that would set me back.  In the back of my head though I was wondering how hard it would be to build something like this myself and the costs of it.  Well something like this from Veterinary Ventures is probally what the wife wants.

Only 45$ I am sure I can make something for a lot cheaper, maybe not as refined but still serving the same purpose.  And why do I have a feeling that we had purchased something like this for our first cat before we got rid of it.  Hmm wonder now if we got rid of that, we still had the "automatic" cat litter cleaner.  Yea that worked great never recommend that to anyone.

Well I will do some searching and see what else I can come up with and start my building just for fun anyway.  
I would like it battery operated so no wires anywhere,  maybe add some charcoal for filtering. I would like to to have a storage of few ounces of water so it does not have to be constantly refilled.

I know I saw a few over on instructables so that will be a good start.