I am understanding you well. Most producers I know go out of their way to sell only what you pay for. If they give you something not ordered. then it will be as a bakers dozen type deal or of a higher value fish. It is bad business practice to sell a species that is widely considered a pest in its pure form. GSF are well known for being a pain the butt.
As appears to be case otherwise, they are very good at colonizing ponds without help from humans. As a kid we had a dozen ponds scattered about the farm. About 2/3's of those ponds had GSF even though we did not stock them into the ponds. My brother and I were the sanctioned bait bucket stockers and a big bull kept other such people out. We could also find GSF in seasonal frog ponds that were well away from the ponds. The fish got in with the early summer rains, bred to produce a bunch of fry, before whole lot would die in late summer when frog ponds dried out. This only happened when heavy summer rains occurred.
This is a lesson best learned through experience which I will leave you to.
