In case this is helpful for anyone: If you’re willing to do some of the work yourself a place like Bike Sauce or Bike Pirates would work (non profit and run by volunteers). They won’t just straight up do it for you, but they’ll walk you through it/assist.

Edit: it’s been helpfully pointed out you meant car mechanic. But I’ll leave this up partially because it’s funny, and partially in case it’s ever of use to anyone anyway.

Canadian tire will allow external parts. But, I would not do this because non OEM parts quality has degraded to the point there is a 1/3-1/4 chance the new parts won’t work. The situation has gotten so bad shops are losing money replacing he same part 3X with labor.

I think that most of them do? I recall asking a branch of Active Green a year ago and they said they can do it, but they can’t give their usual garage warranty with it (which is fair).

After that, I called around to find an acceptable hourly rate (but how much time something takes is also dependent on the shop and staff).

I used to regularly order my own parts when it was cheaper to get it from rockauto. I would ship it straight to the garage. Are there really garages that stop you from doing that?