As far as I know, they are springfield armory inc mags and I've never seen them at a canadian dealer.
I too quested for a long time for a couple 5/10's as they are perfect for hunting. I ended up getting crafty and made my own from a couple 5/20 norc mags. Cut down , rebent floor plate flanges , trimmed spring to suit and had buddy tig weld a stop plate to the follower.
Was a bit of farkin around but I'm real happy with the ones I made