Not sure the permie way to do it. I ad problems with them on our bell pepper plants. I'm growing two extra plants this year to use as bait to keep them off my broccoli, since they prefer the pepper to broc. You might check around and see if they would prefer pepper to eggplant?
There are "organic" fly traps out there, which you set around the plant base and the
fleas get stuck on the fly paper. Not sure how truly organic, non toxic etc that is. I'm guessing that's not very permie either.