You may be able to buy one from a country, I recently did some research on the compatibility of different region OnePlus 8 Pro's with Canadian carriers, you can see the compatibility info in this comment by me.

If you are on the carrier Rogers I recommend getting the China variant 8 Pro (IN2020 IIRC), you can frequently find that for decently cheap prices, otherwise I recommend getting the North America variant (IN2025).

The North America variant is a lot cheaper in the US than in Canada, so you might want to try and get one from the US.