The green snakes are a good idea, but my understanding is that they're hard to keep alive for more than a couple of years - maybe have tough UV requirements? I'm not sure where you are, but if you're in the SW USA take a look at shovel snakes, sand snakes, and ground snakes - there are posts back in the archives of this forum on all of them. They might not be great handling snakes, though. You could always go for a common garter snake and feed it on mostly worms - garters can tame down well for handling, but they'll go through a lot of worms if you don't mix in vertebrate prey.

Billy
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Phillyherping