Think I have a couple of unpainted giant ones in my tool chests or drawers full of unpainted minis...sigh
didn't gamesworkshop do such a critter at some time? I know they made some medium sized snakes that I have
All the snakes you will ever need. If you want to get fancy get some empty large miniatures bases and glue one of the big guys to it, or even a pile of the little guys to make a swarm.