With the Patch 3.1 patch notes as long as they are, even we miss a lot of the little things that crop up in them. Luckily, I was reading Kaliope's WoW Crafting Blog (which is fantastic) and happened to spot this little tidbit: All Engineers, regardless of specialization, will be able to get their hands on both Lil' Smoky and the Pet Bombling. You don't need to do the repeatable quest(s) for them and pray to the RNG gods anymore, either.
The schemata for Lil' Smoky and the Pet Bombling are now Bind on Pickup drops from Gnomeregan. I know, I know, Gnomeregan is terrible, but most pet collectors are so overleveled for that place that this new method of getting the recipes should be dramatically easier. The Pet Bombling appears to be a 100% drop off of Thermaplugg, the final boss of the dungeon. Lil' Smoky is slightly less reliable, but not by much. He drops off of the Arcane Nullifiers and only the Arcane Nullifiers, as far as testers have found. That makes sense, considering Lil' Smoky shares their model.
If you're going to be hunting down these bad (and smelly) boys come patch 3.1, Gnomeregan is the place to be. Kaliope even has some further advice on tracking down Lil' Smoky, should you need it. Good luck on your hunt!