One of the more common places to find locks is eBay but of course it helps to be a “seasoned” lock collector to avoid fakes or uninteresting locks. There are a few lock shows in the US (Los Angeles area; Lancaster Pennsylvania; Indianapolis; and Bristol Connecticut). I don’t know about Canada.
There are a couple of lock collecting journals: Journal of Lock Collecting, for the American Lock Collectors Association, and the Antique Lock Collector for the West Coast Lock Collectors Association. I know the latter sells back issues on CD-ROM and this might be educational.
Useful books include The Padlock Collector by Frank Arnall (sixth edition) and Locks and Lockmakers of America. I’m sure others here have other suggestions.
If you have antique stores in your area this can be a possible source but usually they have a small number, if any.