Oh my. I love maps, especially old ones.
The 1:10,000 topos are no longer available from the MNR as stated which is annoying. Now you have to get them from retail establishments. The last time I looked at the MNR site regarding them, I saw a list of places that sold them.
As far as hard copies of old maps, University libraries are a good source. I found a bunch of old stuff at the Queens Library, but you'd probably find just as much or more at U of T, McMaster etc...
Also, this, It mostly covers Southern Ontario and is a bit older than what you're looking for but what the hell:http://digital.library.mcgill.ca/county ... frames.php