Maybe check with some grocery stores? Grocery stores here in Texas sell live ones in the early Spring, but those are the big cooking/eating sized ones. That may not be what you are looking for.
Also, are you sure you don't already have crawfish? I have always heard that in the South if there is water then there is crawfish. You might get a crawfish trap on Amazon just to check. If you don't catch any in your pond you could always take the trap to a creek or lake in your area and catch some. Dog food in a sock is great crawfish attractant.
Amazon Crawfish Trap
