Replacement part for side-mount window

Looks like the plastic anti-friction worn such that the slide is no longer contained by the lip of the fixed part.
Markings: Truth 307448 or 30744B on the 45 degree arm. 40631G is the number on the slide now missing the plastic anti-friction.
Now I have right and left windows so I would imagine that the other is about to fail, thus would like to replace both. If you have in stainless steel, that would even be better.