It’s taken more than a decade, but the US Department of Agriculture (USDA) has finally released an updated Plant Hardiness Zone Map that spans the nation and the territory of Puerto Rico in such detail that gardeners can now zoom right into their local areas.
It’s incredibly challenging at times to find genetically diverse native plants rather than nativars and cultivar exotics. Depending on where you are, there is likely to be some regulation about the plants that are saleable - I have a 500+ page document outlining all plant material regulations for each US state which covers banned species/listed invasives, requirements for shipping with substrates, and a host of other regulations that govern what plants I’m allowed to ship where, and how.
My advice would be to go to some of the smaller mom & pop nurseries around you (if possible) and ask about how they grow their perennials - do they grow from seed, or from plugs? If from plugs, can they tell you their source nursery? Do they know a grower who focuses their operation on less showy natives, or who does restoration work?
Is there a native plant society in your area? If so, get in touch with or join them. They’re likely to have resources you can draw upon, and more likely to do plant swaps and seed exchanges. If you’re in the US, see if your state has a state nursery you can order plants from. Our state doesn’t have one, but the Master Gardener programs run plant sales to fund their community work and that’s another good way to get native plants with a bonus of supporting the community.