Blackbox customs could make it.
Honestly just take a scribe and scratch it into the pot metal black dust covers. Should look decent.
So, given that none of the retailers that I've found online with these ejection port covers will ship to Canada, is it legal to have someone in the U.S. buy one and mail it to me, or is this innocuous little flat piece of stamped metal a controlled product that has to be purchased through a proper licensed business or importer?
No. Must be properly exported or there is the risk of WW3. Streets running with blood. But still no.
Do a bulk order through azte ch armory. $35 for the import. If 10 buy, $3.50 extra each.