There are two main spots where you can find it. The First One is the "two yak" one, but only two critters can bè killed for a spawn chance once every 5-7 minutes. Thecsecon one is near the starting point, i don't Remember the name, but it's near the shipwrecked boats an the pools where an elemental ...
A potential counter would be [pet]Blue Dragonhawk Hatchling[/pet] enough resilient versus Flying abilities and some potiential counters against decoy with flamethrower dot effect and multiple quills attack. Bear in mind that flamethrower+Conflagrate combo can be devastating against mechanical!
Little Tommy Newcomer
I remember the first time i challenged Him how brutal was his Li'l Oondasta pet eradicating my team in less than 5 rounds.
It took me a while to figure how to defeat him.
I'll suggest a mini carpet pet, Tassy, magical, s/s breed with a mix of mechanical, magic and flying abilites like Lift-Off, Cyclone, Thunderstorm, Nether Gate, maybe a little op moveset balanced via an extremely low droprate from the Conclave of Wind encounter in The trone of the Four Winds.
http://i57.tinypic.com/117zl2o.jpg Surely the Disgusting oozeling is my favourite friend. It was the first one i did ever collect back in vanilla times. I still remember the day i opened a scum covered bag ad it appeared to me. People offered me a lot of gold for it but I knew it would have been th...