This won't work anyway. Fleas easily jump out of water, soap or no. The only water that kills fleas is boiling water. I used to use a flea comb on my cats and had to have a dish of REALLY hot water next to me while doing it. If the water cooled, it had to be heated up again.
Don't know about the commercial flea trap, but I wouldn't count on it working very well, either. If your home/RV is infested, diatomaceous earth worked into the carpets is effective (wear a mask and move pets out while applying). It works for any pests with an exoskeleton: fleas, ants, cockroaches, etc.