In the Los Angeles area, El Rey Farms from Hatch New Mexico delivers truck loads a hatch chilies once a week to a location at La Puente High School beginning about Aug 20 through late September on Saturdays. Big crowds, great chile.
About $40 for a 38 pound sack. You can find them at http://elreyfarms.com/
Though they will roast them for you on the site for a small fee, I prefer to do it myself on the gas grill/or the charcoal grill, depending on what taste I want. I still have about 5lbs in the freezer from last year. I bought about 70 lbs this year. There is usually some interesting discussions with my wife during this time of year (re:space in freezer)