If that's the case, have UPS ship to their warehouse near the border and nip over and pick it up. I used to do that with R compound tires. A certain company (Kal Tire) had an exclusive on Nitto tires in Canada, and they added like 50% markup. So I'd order from Discount tire, shipped to UPS warehouse in Fort Erie, and I'd pick them up there. Cross the border, pay your GST, done.
This was my plan also. I am planning a trip to to Washington State at the end of June. I was hoping to find one supplier for all the items I needed in order to simplify things. But 2 orders (MGW & CJ Pony Parts) is doable.