As noted above, there are several in a West Seattle dive site, but the silt makes photographing tough. We are a group of photographers and made six dives in Hood Canal last week, and had GPO's on all dives. Conditions were not good for DSLR photographers, but the video guys were able to get some shots of females on eggs in their dens. Several of us are heading back over this weekend for some more photography (also many wolf eel, all manner of rockfisk, nudi's, lings, cabezon, jellies, etc).
If you are interested, feel free to send a PM and we can try to link you up with one of our trips. We are starting to plan a night dive with the same operator (Pacific Adventure) later this Fall with the hopes of photographing GPO's out in the open.
Will trade GPO opportunities up here for humbold squid photo ops in your area.
Cheers,
Dan