It really depends on what material you're painting over, and what you need the top coat to do.
If you're painting over wood, where water intrusion is big concern, you want to look at something like epoxy or Dick Nite's original urethane. I've use epoxy, and I know it works. I haven't used the original Dick Nite's urethane, but others here swear by it (and sometime at it). Hahaha
If you're painting over plastic, resin, or PVC, where water isn't a threat to the lure, you can use a water borne urethane because you're only trying to protect the paint scheme from the water.