This is the item I am referring to (sorry that I don't know / am too lazy to embed the link): http://mop.wowhead.com/item=46767#comments
The item was from a Mountain Dew promotion and is a pet that you fuel with either Red Fuel or Blue Fuel. If it meets another Warbot of the same color, they become friends. If they meet the opposite color, they fight.
Anyway, previously there was no way to get this item unless you took part in the Mountain Dew promotion. However, just recently (ie patch 5.0.4) it was re-added to the game.
It is sold at the same places where you buy your toys (ie Toy Train Set). A neutral vendor is at Dalaran (http://mop.wowhead.com/npc=29478).
Anyway, just watch out for it and don't end up buying it at a ridiculous price (like 25k) because you think it's discontinued.
Or if you're rather unscrupulous, you could buy them and advertise them for more than what it costs (350 with Kirin Tor Exalted).