Available at these Costco stores:

In alphabetical order: 

Alaska
Anchorage, Warehouse 10
NE Anchorage, Warehouse 63

California
Citrus Heights, Warehouse 771
Folsom, Warehouse 765
Novato, Warehouse 141
Roseville, Warehouse 29
Rohnert Park, Warehouse 659
Sacramento (Cal Expo), Warehouse 471
Santa Cruz, Warehouse 149
Santa Rosa, Warehouse 41
Woodland, Warehouse 1003

Idaho
Coeur D' Alene, Warehouse 773
Meridian, Warehouse 1343

Nevada
Reno, Warehouse 25

Oregon
Bend, Warehouse 101
Central Point, Warehouse 1287
Clackamas, Warehouse 97
Eugene, Warehouse 17
Portland, Warehouse 2  
Salem, Warehouse 68 
Tigard, Warehouse 111

Washington
Aurora Village, Warehouse 106
Burlington, Warehouse 662
Issaquah, Warehouse 110
Kennewick, Warehouse 486
Seattle, Warehouse 1
Spokane, Warehouse 670
N Spokane, Warehouse 1298
Tukwila, Warehouse 6
Tumwater, Warehouse 64
Vancouver, Warehouse 772