Morton puts out a curing salt, but I've only seen it in stores in the midwest. You can order it online, but I should think local stores would carry it. Maybe a vendor in Berkeley Bowl could order it for you.
I thought corned beef was just soaked in a brine solution using NaCl and assorted other herbs and spices. Sodium Nitrate is for preserved meat. I believe the corn refers to the size of the crystals of salt used.
Doesn't seem to bother Sara Moulton. http://www.foodnetwork.com/recipes/sa... Apparently, you pays your money and you takes your chances. Nitrates for pinker meat but the possible risk or more salt and it's risk and greyer meat.