Cheap milsurp ammo is long gone. .393 British hasn't been used by anybody for eons either. There has never been case lots of .30 M2 ball in Canada. A box or two might appear at a gun shows, but not recently and not in any great quantity.
Modernish milsurp ammo like 7.62 x 54R is being kept out of the country by civil servant policy.
Reloading is your best alternative. Still isn't exactly cheap but it's far less than factory.
What? Did that case of x54 just magically appear in my basement?