I know this is probably too late, but you can order flightless fruit flies from Big Apple Herp- Which is a pretty good place, it's always recommended to me. I just raised some tadpoles and their '
D. melanogaster Complete Fruit Fly Culture Kit' worked great, I just needed a few extra tubes to supplement the fly breeding time. It's also something that they only overnight. So it would get to you quickly. I would say call them to order it so they are sure to get it out same day- if you do order. And since they're soooo tiny, maybe just get one tube to see if they're not too big still
I'm having a hard time finding pictures that show their size...
http://www.openscience.it/droscarta.jpgThis is about the best I could do.
I really don't know why they're there- but I do know that Toads can lay in some amazingly shallow and scarce water.
...this is a totally uneducated guess, but can some toad species lay eggs in mosit soil? I know some frogs do some pretty crazy things. What part of the country are you in?