There is of course the Rhododendron Species Botanical Garden that is 25 minutes south of Seattle, though you'll have to pay extra for a Phytosanitary certificate if you live on the Canadian side of the border. The botanical garden only offers this at certain designated times, usually in the Spring. Once you have the Phytosanitary Certificate, they will let you take it across the border.
Isn’t there a person who drives up to UBC garden and customers pick up during strict hours (as in limited … be there)
Meanwhile —- some recent photos of native « wild forest » Rhodos which are protected strictly here in BC