By your inquiry to avoid duty I assume you've never heard of Point Roberts. if so you've been missing out. It is a tiny peninsula near Tsawwassen that is US property. Its only 20 mins from my office in Richmond or 40 mins from Kits (assuming no traffic).
There's a few companies in Point Roberts that act as receivers for your packages. I use
http://www.tsbshipping.com yet have been tempted to switch to
http://www.thelettercarrier.com/ since it is walking distance to the border. They will sign for your package then send you an email confirming it has arrived. You cross the border, pay them a small fee for this service, then return with your package (and a tank full of cheap gas!).
Always declare your goods! They know why you crossed, be honest and they won't ding you with duty/taxes most of the time. I've crossed with $600 once and got waived through. I think I am over $5000 of stuff I've picked up without having to pay tax, and only $1500 I've had to pay tax on (and never duty!).
Sometimes there are really long lineups to cross, so being able to park and walk across is handy, thus why I may switch. Just means no tank of cheap gas, yet also no 20-30 min wait.
The same services are offered in Blaine. Its just further to that border from where we live/work.
d the other a trip.