If you can rent a car for the day, you can drive up to Blaine, WA. The office there normally is wide open for availability. It is just under 2 hours each way. It's on the American side so you won't have to cross over and back as well, and you could get the interview completed that way. That said, you will still have to go to an office in Canada, one with the iris scan available, to use NEXUS at the airports in Canada, though you can do this right after the interview in Blaine. You could also look at driving across the border up to the office at YVR, or the office in downtown Vancouver, both of which would have the iris scanning available, although I don't know how their appointment availability looks.