If you're willing to drive a bit, Jackel Enterprises in Watsonville usually has a good supply of WRC, including longer stock. They also carry AYC, but normally not more than a few boards. Look up their web site on Google and give them a call to see just what is available.

They may also have Sitka spruce, but I don't think so. Aircraft Spruce and Specialty mail order aircraft grade stock at very high prices, but they also have a 'bargain bundle' of random cutoffs. I got one some time ago ($15 at the time, probably the same now) and it had more than enough for the deck beams for a Greenland boat except for the masik and footbrace - no 2" stock. I wouldn't get too hung up on the Sitka spruce though. Any decent quality wood should work fine.