Key resource for optimizing pollinator habitats - https://www.nwf.org/Garden-for-Wildlife/About/Native-Plants/keystone-plants-by-ecoregion. Pick your region and pick some of the keystone herbaceous perennials for bees, then find species you like that are native or near-native to your region in those genera.
Native Allium has had a lot of success for me; I've seen a variety of bumble bee, wasps, carpenter bees, and cuckoo bees on them this year. My Monardas and coneflowers are always very popular. I've seen some decent activity on my Gaillardias too. Unfortunately I haven't seen much activity on my non-cultivar sunflowers but the little activity I have seen has included some really interesting Ichneumonoid wasps.
Zone 5b northern plains
Check with your local native plant societies. They may be willing to advertise your stock to their members or let you set a booth up at events. You could try Nextdoor or Facebook as well. If you or someone you know is planning a garage/yard sale, set up a table with your plants there.