My suggestions on the above...
Make it easier on yourself to purge the crayfish.
Buy two galvanized wash tubs. They are inexpensive, so it won't cost much. Take one, a big friggin screwdriver or punch, and a hammer, and make one into the largest collander you've ever seen by punching it full of holes. I suggest punching from inside to outside, to keep the sharp edges away from the live food you'll be putting in this collander.
Put the collander into the unpunched one... And then pour in the crawfish from the bag. Fill it with water from a hoze, and sprinkle on several cups of salt. You are not seasoning them here, you are making them empty their digestive tract!
After about 30 minutes lift the inner tub out, and give them a quick wash with the hose. No problems having to fish out live crawfish from a pool.
Any place that does a crawfish boil, buys crawfish live, and will be happy to make a few bucks selling to you. I know that Nate's (
http://www.natesseafood.com/index.cfm )does a nice boil, and sells bags as well. Make sure to call about a week ahead, so that they order enough to have some to sell to you.