I don't think very many places sell seeds. Why not go out and harvest your own seeds?
One good place to buy bulrush rootstock is Wildlife Nurseries Inc, POB 2724 Oshkosh, WI 54903 920-231-3780. They have: Hardstem, Softstem, 3-square, Green, River, Alkali bulrushes and woolgrass (Scirpus cyperinus). They also have Flowering rush-Butomus umbellatus, Soft rush-Juncus effusus, and Torrey's rush Juncus torreyi.
The hardstem and soft stem bulrush spread pretty fast thus unless you want expansive areas covered it would not take very many plantings to colonize a pretty large area. 300 roots = abt $117
FYI: Woolgrass:
http://www.illinoiswildflowers.info/grasses/plants/wool_grass.htm
