Several other ag airplanes (Air Tractor, Dromader, Ag Husky, Weatherly) look a little like a Pawnee, superficially at least.
If you are determined to fly the Pawnee, it should not be that difficult or expensive if you follow these steps:
(1) learn to fly tailwheel;
(2) get accepted as a tow pilot at your local gliding club;
(3) build up experience on a Supercub, Citabria or similar tow plane;
(4) track down a glider club with a Pawnee, volunteer there, and impress them with your past experience.