you live in Canucklia every podunk hardware and auto store has a metric fastener assortment. they are short little buggers though. I do NOT recommend this but have found many sheet metal screws holding that cover on to "barn bikes".
If you have buy a longer one and cut it shorter, run a nut on the screw BEFORE you cut it off, makes a great guide (you can clamp it in the vice too) and it reforms the last thread when you take it off.