Precision scale would be a source for detail parts. Mechanical parts would be more of a problem.
I had for time a Westside PRR H6sb that also had the narrow tires. They were about 1/3 narrower than all my other stuff. At the time I had a layout in my basement with handlaid track. As with most basement layouts, the changes in the weather caused the wood to shift some - in the fall and in the spring.
I also had a USHobbies Mikado. When I got the H6, I had to narrow the gauge on all my curves to keep it on the track. then the mikado would not go around the curves! I finally spent a summer regauging and fiddling so I had both engines staying on the track. But as soon as the weather changed that fall, the H6 started derailing again.
I finally traded it for an old Max Grey PRR 4-4-0 that the owner said would not pull anything. We were both happy with the change. I told him about the narrow tires too.