Funny you mention this because I searched the site last night to see if there was another thread about wiper refills.
None of the local parts stores here carry them any more either...My 73 New Yorker has 16" blades and I was able to find some 17" refills at Princess Auto which is kinda like Harbor Freight in the US.

I just looked at the packaging and they were rebranded Napa refills, I searched the Napa site for "wiper refills" and a bunch came up so they must still have them.