Thanks all for your help. I'm in the trucking industry, and know the carrier who hauls from the UPS warehouse in Sweetgrass for points in Alberta. I've had Corbin ship via UPS to this warehouse, and I'll get the seat the next day that it arrives there. I'll give the driver money for the GST, and leave him with a bit of extra.
It seems that Corbin and this Canadian distributer have come to some kind of "arrangement". The distributer has dropped all of his other lines to deal exclusively Corbin
(distributer change), and Corbin won't ship to Canada. I never did check with the "approximately 7000" dealers in the US - that was a good idea. Funny that Canada only gets one.
The seat costs $450 direct, and the price quoted by the guy in Burnaby was $550. I assume that Corbin gives him a fair wholesale price, so the rest is just taking advantage of his situation. The backrest was $250, and he quoted $300. The exchange is very close now, so this is really excessive, plus GST has to be paid on the increased amount. Corbin charged me $25 for shipping, and he wanted $45 to Burnaby, plus the shipping from there to my place in Alberta.
OK, I'm done with my rant - I feel better!!!

If anybody needs help getting around this, I'll see if I can find other carriers that haul UPS into other parts of Canada.
Again, thanks for your help.