Silver Platters is WAY expensive (and they exist in Bellevue, Northgate, Southcenter and I think one other place. Don't go there. You'll be better off buying online.
For hard to find stuff, you can try the used section at Singles Going Steady downtown on 2nd Ave.
Other than that, good luck and let me know what you find! There isn't much.
Wait.. go to Vancouver... Scrape Records. Best record I've ever been in.