Saturday morning I bought some very nice milpero tomatillos from Hector's Honey at the Healdsburg famers market. They're $1.50 per basket. The lady at the stand was surprised that I was familiar with them (thank you, chowhounds!). I used them in a luscious chile verde, and am looking forward to buying more for a salsa en molcajete.
Hector's also sells at the Santa Rosa farmers markets on Wednesdays and Saturdays. Don't know if they sell direct at the farm, but here's the link for contact info.
2794 Fulton Road, Fulton, CA