Rancho Gordo beans carries Red Crimson popcorn. Their products are available in the Bay Area, though not in WC. Everything they offer is amazing. Their shipping is quite reasonable at $8 flat rate per order in that you can stock up on their truly incredible beans and hominy and just pay a flat shipping free.
1924 Yajome St, Napa, CA 94559
Not sure what you mean by "heirloom."
Berkeley Bowl sells popcorn on the cob. It is about $1.50 for a bundle of three. They are not marked "popcorn" as such -- I'm sure most people just buy them for decoration
I bought the small red cobs. You put one of these (the whole cob, without the husks) in a small paper bag and microwave it until it pops.
Be careful -- if you overcook it, it will catch on fire-- very bad.
2020 Oregon St, Berkeley, CA 94703