Apart from the stock centers, the only other commercial source of
Arabidopsis seeds is Herbiseed, The Nurseries, Billingbear Park,
Wokingham, RG11 5RY, England. Their FAX no. is 44 3 44 868335. I
have not checked recently, but they sell a local ecotype of
Arabidopsis for use in overseeding of herbicide screening plots.
Their price was about 40 English Pounds for 25 grams in their
1990 catalog, so if you are not concerned about the background,
this might be a good bet.