I hear ya! I go through the same thing here in Vancouver, BC! There are two places that I have been able to find here; Michaels or Scoop and Save. Scoop and Save is about 45 minutes away and I have to drive over a toll bridge AND they're not open on Sundays! Michaels doesn't really carry all that much. I find myself driving across the USA border to pick up things but then that is inconvenient, too, and the Michaels there doesnt always have what I need in stock. I did, however, find a great company a couple of weeks ago www.vanillafoodcompany.ca . They are based out of Markham, ON and I found their prices to be decent. AND they only charge $7.00 flat fee for shipping to Canada. I actually needed my items quickly so I upgraded my shipping but I received my items in two days so the extra $8.00 in shipping was totally worth it. I ordered my cupcake trays from a company in the US and have them shipped to a receiving company across the border and I drive over and pick them up.....saves me a ton of money! The plastic clamshell containers that hold 12 regular sized cupcakes costs me $2.50 locally but when I order them from the US and pick them up across the line they only end up costing me $1.00 each and that includes the cost of shipping! That's a big savings! I find there is not only limited supply here but the stuff you can get here is super expensive! I've mentioned to my husband a couple of times that we should consider opening a cake supply business! LOL!
Funny how it works, I moved from Vancouver to Lynden, and I cross the border to go back to scoop and save :) There are zero cake decorating stores here, except Michael's, if you count that, and Langley is closer than Seattle.