Well i know you can use like a small coke bottle that you get out of a vending machine.. cut just the top part off just so the damsel can fit and you can put food in the coke bottle and if he is hungry enough he should go in. Also call around to your local LFS for a fish trap, where i worked in dallas rented them out. Its basically a cylinder with a trap door. But it has a place for food and then you put it in the tank and you control the trap door.
