I have seen some reptile looking prints, usually kind of "slinky", stretchy fabric in the clothing/garment area of the local Joanne and Hancocks. If you could find something like this just make a tube with sort of a hoodie to go over his head and make a really long tail and of course, a red felt forked tongue!

On the tail, you might want to make some rattles (pieces of material with gravel in them) so that when he wants he could shake his tail & it would rattle.