The moon nymph is a repeating random event, so yes, you'll have a chance to recruit a new one later. In the future there will be fixed point of interest that'll allow you to recruit one or two, similar to the raccoon bandit camp, wolf den, etc.
All you need is Lavaheart gems to learn the recipe for dragon potions, found in the same location as the quest. Fox romancers I don't remember off the top of my head but I think you have to pass a flirtation check or, failing that, gift them some wine.