All three items are currently being sold from toy vendors in Dalaran and SW/Orgrimmar on the beta. The pet costs 400 gold and the fuel costs 20 silver.
Side note: I wasn't able to check if there are any differences between the original Warbot and the vendored one. The pet is unique, so I can't have more than one in my journal on the beta. I'm going to guess that there's no difference, though.
Finding it on a vendor is an interesting turn of events since the recipes for both the Warbot and the fuel still exist. Perhaps there will be two sources for these items - we'll be able to purchase it from the vendor or craft them ourselves? Or maybe the vendored pet and fuel are simply placeholders and for testing purposes, while the actual way of obtaining the Warbot and fuel will still be from Engineering and Cooking?
Things could change between now and release. We'll have to wait and see where this pet will wind up.
As far as I can tell, the Warbot and fuel won't be available until MoP, but maybe we'll get a surprise come Patch 5.0.4.
Oh and last but not least, two Warbots battling each other (not in an official Pet Battle, but just idling after being fueled up) don't reduce their health in the Pet Journal. Battling bots, go! ;)