I've been to Record Surplus (on Pico, near former Poptopia/IPO showcase
the Gig) quite a few times but never struck gold, tho found some nice
vinyl.

I suggest Amoeba on Sunset - it's even bigger than the Haight store in 
SF, where I've never left without several rare pop gems (usually at 
thrift store prices). LA does have a much, much larger pop contingent, 
though their massive turnover should negate the picked-over factor.

 - michael