Jubilee Park in Spruce Grove, had Ohio Buckeye nuts, and could have been Tartarian Maple seeds galore last fall.

I'm too late for this Spring, but I suggest that you try the following places:

-the river valley; it has a warmer microclimate and you can find a whole array of invasives. I live in the Peace River valley, and the Amur maples have certainly arrived for good. I hate the things, but do have to admit that the flowers are lovely.

-the U of A botanic garden. They might even give you seeds of hardy cultivars if you ask!

-Have you thought about going to Waterton and trying to get seeds of Douglas Maples? They're lovely trees and far too underplanted. I probably don't have a chance in 2b, but Edmonton should be warm enough to try.