The only clover (Trifolium species) native in Maryland is a habitat specialist (one that isn't replicated in home gardens) that is state-rare/threatened and as such is not commercially available. Several native plant nurseries might sell Sedge seed, but more commonly they are available as plugs or larger potted plants. Extension doesn't collect information on plant suppliers, nor do we recommend particular businesses, so unfortunately we can't point you towards any sources. Several of the major native plant seed suppliers who probably do sell some species in bulk are located in the prairie states, and their genetic source of plants (provenance of the seed) is probably not local, which might impact the long-term survival of the plants or their ability to thrive (if they are not as heat-hardy or tolerant of high humidity and clay soils, for example).

Miri