WoWDB

They spawn all around Karazhan, a few even on top of the lower towers.
It's best to look for them in the early hours or after maintenance, when there aren't many people around. Otherwise you'll have to depend on luck.

While you're there, don't forget to defeat the nearby pet tamer and get your daily supply sack!

This little guy is a bit of a pain to catch, so be ready for some long camping hours or some beautiful luck ^^ despite rumours, they do spawn at random during all hours, there is no set timer that the pet collectors have found, but once you get him he does could towards achievements so well worth seeking him out even if you aren't an avid pet collector ^^