The fridge trick worked like a charm! We caught 2 house flies and cooled them down and dropped them in with no problem. Our little fatty ate 2 fat house flies and at least 8 fruit flies. At one point he was munching on 3 ff at a time.
Do you order fly pupa or do some pet stores carry them?
I saw fruit fly cultures near the mealworms at petco but they looked too tiny for my ghost (it is about the size of my thumbnail and can take 1/4 inch crickets.)
Mantisplace.com (Rebecca) is one of best places to get all types of flying feeders from, I've been using her for years, plus her prices are on the low end of the scale.