I bought one from OSH in Los Angeles, them seem to carry a few of them, but not always in stock.

I've also seen them at farmer's markets.

My favorite source, however, is the bulk bin at Whole Foods. The little dried fruits are full of viable seeds. Yeah, you'll wait 3 years for fruit but I just scavenge what's been spilled by careless customers, so seeds are free as far as I'm concerned.

I've also grown scarlet runner bean scavenged from whole foods floor. Recently scored a handful of buckwheat - gonna try a fall crop for seed for a big green manure crop next spring.

Anyway, unless you want instant gratification, try the bulk bins. A dedicated individual could grow an entire farm from their stuff.

I've seen them at Lowe's in Escondido in previous years.