Try Well Sweep Herb farm.

In a recent issue of Horticulture magazine, I came across a reference to your plant, but since I don't have the magazine on hand I did a search on the Internet and found a source for another variety, which is touted to be "better."

The variety is Sanguinaria canadensis 'Multiplex' (Double Flowered Bloodroot)

Unfortunately, so is the price - $28.00.

Hope this information is useful!

Bill

Here is a link that might be useful: Plantdelights

McClure and Zimmerman are offering it as S. canadensis var. Flore Pleno for slightly less - 24.95 (ouch). www.mzbulb.com

...many nurseries with this plant will not ship to California. If anyone is looking for this or other plants, UC Botanical garden will send seeds if you write and ask them for the plants you are seeking. Sanguinaria canadensis 'Plena' is on their list of available plants.

Here is a link that might be useful: UC Botanical Gardens