Most chain pet stores that i see dont really carry those so they may be hard to find. But there are plenty of sites to order one from or you can just Google local fish shops and try your luck there.
No person shall import, export, own or possess, acquire or dispose of live piranha fish (Serrasalmus, Rooseveltiella, or Pyrocentrus), grass carp, (Ctenohparyngodon idella) or hybrid grass carp within the state without a license or permit issued at the discretion of the department for scientific, biological, or exhibition purposes.
Where does it say you can have them for the private home aquaria?
He is not a scientist or doing scientific research, that rules out scientific and most likely biological also.....and he's not a public aquarium or zoo or any other type of public exhibit.
It's all in the writing of the application. The triploid carp permit application is intended for private farm-pond owners. The department authorized the application to include Ps as a 'write-in' on the triploid carp application for private property ownership or possession.
BTW, where does it say anywhere; "Public exhibition purposes"?