According to this (incomplete map, but gives a good idea): http://www.waldeneffect.org/blog/Black_soldier_fly_101/

You border a state that reportedly has the species locally. You can try the different methods to attract them from the environment since you are on a bordering state; there may be some colonies in your state from time to time. It's worth a shot.

If not, google around you will find some sellers. Also, BSFman can chime in, he's the resident expert on such things!