If you have the time, my advice is to start by harvesting the seed you have available (being conscientious about not taking all the seed from any population, of course) and establishing small restoration plots. After a few years, those small restorations will start to function as additional seed harvest resources and you can start to build slightly larger restored plots with that seed plus wild-harvested seed. As you start looking, you're likely to find more harvest sites and species in the area. Eventually, you can build to the point of being able to harvest and plant at the scale you want. This could take 10 -15 years or so, though, so it's not a quick solution. On the other hand, it's a tried and true method in many parts of the former prairie in the central U.S.