The local Ace Hardware and the Trustworthy Hardware have the Robertson
square drive screws and drivers.  Both stores called them "Canadian"
screws when I enquired as to availability.

Also the little hex bits that go into a magnetic tip screwdriver or
power drill driver were available at both places.  These are _common_
things, not exotic hardware.  If your hardware store doesn't stock these
they are in the Dark Ages !

Scott Olson