Canada does not require tests to enter Canada but DOES require testing to cruise. So- 2 days out it appears to be. Have you considered a computer monitored test like https://rapidtestandtrace.com? You use whatever test you have (I think they accept almost all of them) make an appoint to zoom, and do the test online. Otherwise, there are certainly places in Seattle where you can get the tests done and you may be close enough to walk- I'd check your hotel, they probably can help.