Ressan the Needler can be found with NPCScan. You will need to add it, his NPCScan ID is 10357.
You can also use this macro to help find and tame him:
/tar Ressan the Needler
/cast Tame Beast
I'm not sure on his exact spawn timer, but before Cataclysm it was between 1.5-2.5 hours. I believe it is much shorter than that now, probably more like somewhere in the 30 min range.