In a pinch I would make my own 'yarn mops' and tie with a cork or piece of styrofoam so it would hang from top of tank to almost the bottom. http://members.aol.com/WnyZman/mops.html
If you have only platties and mollies, they wont eat many of the babies if you have enough plants and FLOATING PLANTS. Breeding traps are a bad idea. Stressful to the parent fish and the water quality is bad for the babies. Babies worm their way through the holes in the net traps. So I say plants. If you have a community tank, you could just try to catch the babies with a net and move them into a seperate aquarium.