Plenty of good shops up there. Call a few and ask about there work and prices.
Have an idea of what you want and see who you click with.
Not many people in the US know of the builders in CAN.
Call some of the big sled guys too. They may be willing to do a atv engine.
I just bought a used 2016 Yamaha YFZ 450 R a few days ago. It’s practically brand new less than 20 hours on it. I noticed the light knocking noise in the motor is that common on these machines? That’s kind of what I’ve been hearing.