Hang around a construction site and get the five finger discount.
I find HD to hit and miss with alot of stuff I need at work... really annoying. An associate can typically check stock of other area HD's in real time if you ask, they've done this for me before. Maybe they could direct you to an HD that has stock. Remember, it will be the furthest one.
Lowes only just started opening stores in Canada, so I'm not sure about them.