Time to start talking with the dealers that supply the target shooters, to see if they know anyone that knows anyone that... Well, you get the picture.
Some of the dealers that sell the target stuff are pretty much operating out of their garages and basements anyways. The more of them you can reach, the better the odds that someone will have a contact.
That's where I'd start, anyway.
Why? Not much point in knowing that you can never get another box of the 'perfect' ammo, is there?
Cheers
Trev