When I started plotting, it took me a while to find local seed, fertilizer, lime and chemical sources. As Jack said, it will probably be your local Farmer coop's. Talk with local farmers, check with local garden shops and your county extension agents, they will point you in the right direction. When you find a place, don't be afraid to ask for what seed etc you are looking for. Most places can order what you are looking for if they don't have it in stock or they will tell you where to get it.