If you want a source for Monkey Flower, - or any other wetland native for that matter, check out Environmental Concern, a non-profit nursery out of St. Michaels, MD.
http://www.wetland.orgTheir catalog is online. They are for the most part a wholesale supplier for projects related to the restoration of the Chesapeake Bay; however, they will sell to retail customers and will ship. They have reasonable prices and a super friendly and well informed staff.
I have purchased swamp rose, marsh hibiscus, and sweet flag from them. I will be getting a few hundred plugs of pickerel weed and arrow arum soon. I can't recommend them highly enough.
Brian