Have you tried H Mart up near Alderwood Mall?
If in a pinch, somewhere closer is HT Market on Aurora Ave.
They have only dried small ones but they work if you put 7 to 10 of them in a tea strainer to make the stock.
There is a Korean Market on University Ave. too but I have never been.
Thanks mchutch, I looked at HT Market but didn't find them. That however does not mean that they weren't there as it is a big store and they could have been somewhere other than the Korean section.
I am substituting shrimp stock from my saved exoskeletons in the freezer. along with the nectar from the clams for my tofu soup.