Here's
one place you can order them.
Cornell has a good site on the bean and the ricin. Another site, for vets, states that the seeds are up to 3% ricin, which is huge, I think you could effectively poison folks just by grinding up the beans and substituting it for some of the flour in breads, rolls, etc, if the poison isn't destroyed by the baking process. Another site states that 3 seeds can kill an adult. The plant is native to Africa and India, but is often used as an ornamental and has become "naturalised" over much of the south. IOW, it grows wild. The oil, which is the only non-toxic part, has long been used as a laxitive and was used as a lubricant, including mixing it with aviation gasoline in the early days of aviation, during WW-I for example. Seeds or started plants should be available at your garden store. I found one site that would sell you 10 seeds for $2, onther had 10 for $1.25 These of course are for ornamental purposes, for agricultural quantities, I suspect the costs are much lower per seed. However a California state site indicated that growing them is very labor intensive, because unlike wheat, milo or soybeans, they don't all ripen at once, so they have to be picked by hand. This means that they are mostly grown in very low labor cost areas, like India for example. Thus getting large quantities of seeds/beans might take some doing, and would surely raise supicions, unless you were a garden seed dealer.
The bulletin said U.S. experts believe ricin is ineffective as an aerosol-based weapon.From http://www.phls.co.uk/topics_az/deliberate_release/pdf/ricin_guidelines.pdf
• Accidental poisoning with ricin has occurred following ingestion of castor oil seeds. Although ricin is poorly absorbed following ingestion, one to three beans chewed by a child, or as few as eight seeds chewed by an adult may be fatal.
• Ricin has been considered as a potential chemical warfare agent. Although non-volatile, aerosols may be inhaled.
There appears to be some disagreement among the experts, but let's hope we don't have to find out who is right.
aristeides-
You may be interested in #14.