Could you make a weekend project of it? There are quite a number of Leafs for sale at any time in the Seattle area, which you can check out on the Carfax reports. Cars that were originally sold and serviced here should have little heat-damage in their batteries. There are moderately priced motels in the Marysville/Arlington area that would put you within fairly easy striking distance of the the dealers in Everett, Edmonds, Seattle and Bellevue, which are target-rich environments (although some, e.g. 405 Motors, seem a little dubious to me, but I didn't ever actually visit there...maybe they just have a few bad Yelp reviews).
If you have a traveling partner and an ICE, I'd try leaving *early* on Saturday, hitting several dealers, then heading back to your top choice on Sunday to negotiate when they open. If it goes poorly after an hour, walk out and go to the second-best car. I may be crazy, but if anyone thinks the tow-eye can take it, I'd be tempted to stretch the range between QCs on the return trip with some towing behind the ICE at the minimum legal speed on I-5, which is what, 45 MPH? Late on a Sunday night that seems like it would be pretty easy.
If you have to travel solo on the bus and rent a car locally for searching, that would make the return a bit of a challenge, not to mention getting up here in time to do much on Saturday (assuming a standard weekend), so I guess that would mean taking an extra day off and staying two nights, not to mention doing an honest QC trip home.