When I go on the WDW site and pick tickets, then Canada, the only AP option is the Premium. If I pick one of the States, I get the option for the regular AP
I had that same problem. So I just waited to buy my AP when I got to WDW on the first day of my trip in Sept. I just used the site for the price by picking one of the States.
I'm sure if you called they would let you buy just the AP. I have no idea what makes them think that everyone from outside of the US all want the premium AP on the website.
I ordered my regular AP over the phone and recieved the exchange voucher about 10 days later by courier. No problem for Canadians. I guess you just need to call.