AFAIK most of the scrap yards in Canada can link to other scrap yards around the country and find out who has what in stock.
If all they did was check their own inventory then maybe you need to make friends with one of them so they'll go out of their way for you and do a search.
The other thing to try is to actually go out to the yard and look for yourself. They may not be inventorying the doors at all and so wouldn't know if they had any on hand or not.
BTW, if you're describing them as 'passenger windows' it may be part of your problem. If it's the opening windows in the Chev/GMC vans then some cargo vans came with opening windows (mostly Chev) and some did not (mostly GMC). Try referring to them differently.
At one point when I'd first bought my GMC van I thought about replacing the fixed windows with the bottom opening windows and contacted Apple Auto Glass. Extremely pricey, like $400.00 a window and they wouldn't install them for me, said I had to find a body shop to do it. BUT the replacement window kits WERE available....that was 4 years ago. Far cheaper to replace the whole door if you can find them.