What you could do is take two 2-liter bottles. Cut the top off of one and the bottom off of another. Stick the top of the one bottle into the bottom of the other with the small end inside, so it creates a funnel. You can glue, or tape the bottoms together. Leave the cap on the outside bottle and you have a basic minnow trap. When you need to get them out just unscrew the the top and shake them out.