I used to buy Loompanics Press books at AMOK Books in Los Feliz. Stewart Swezey still runs the AMOK website. If you like Loompanics, I highly recommend this massive catalogue.
I have a whole collection of vintage SF paperbacks that feature his cover art. It’s a very niche fandom of people (probably dudes) who grew up reading these books in the 60s and 70s.