Looking for Beefeater Summer Gin in SF
You might try calling Cask on Third Street, they seem to take pride in their impressive selection, even though they are in a fairly tight little space. http://www.caskstore.com/ 415.424.4844
However I would NOT recommend special ordering through them unless you're desperate; I gave them my name and number for some Brizard white Creme de Menthe and it's been seriously like three or four months with no call (I found some at Ledger's Liquors in Berkeley). Only buy it if they have it in the store. I have found some very nice bottles there (Hibiki whisky, Germain-Robin brandy, Small Hands grenadine/gum syrup/pineapple gum syrup).
If Cask doesn't have it you might try Ledger's, depending how willing you are to travel. It's maybe a 5 minute walk (if that) from North Berkeley BART, take Delaware west into the neighborhood (away from Sacramento) and then left on Acton in a block or two; Ledger's will be at the corner of University Ave. about three blocks down. I'd call first, obviously, to see if they carry it. They are pretty reliable on special orders in my experience.