Inside the city San Francisco I believe is almost non-existent to find a shop. High Bridge on Mission Street might be the only remaining one. You must go out of the city to find a shop. The surrounding Bay Area has some good ones: Peninsula Guns in San Mateo, south of S.F. perhaps. Triple A Sports in Vallejo is very well stocked. Walmart just has loaded ammo. No Cabela's in CA. Nearest is in Reno Nevada. If you were to be near there...Scheels in Sparks NV (Reno Area). has virtually everything. Great experience too.
There are some very good gun shops in the Sacramento area and a Sportsman Warehouse in Rocklin (Sacramento Area) That's a couple hours north east of the Bay Area.
Coming up in the Bay Area 7/11-12 Fresno Gun show. And Valljeo show 7/18-19. You could find brass, ammo etc. there.

What about ordering what you need online and have it delivered to CA. I don't know of any legal situations to be aware of and what difficulty and cost to get your stuff back to Ireland.
Check out Amazon for brass .357, 33.00... 250 once fired etc. Ammoman.com; TargetSportsUSA.com; plus many others. There are many shops in the Bay Area that have brass. Primers are available and powder is becoming available