If you can find a bait shop you trust, they usually have very good deals on crickets and sell some of the biggest ones around. But be careful, because bait shops aren't the most careful with making sure their bait is feeder quality. I used to buy crickets from this guy who bred his own in the shop and eventually started advertising as selling feeders for reptiles since there were not petstores within 45 minutes of the town I lived in.
I'd never buy worms from a bait shop though, even if there was a great buy. It's just too risky.