Pella window drags on frame at bottom

We have older Pella windows 1976 vintage. The opening mechanism has two rollers at the bottom which should allow the window to be cranked open. The rollers must have worn to the amount that they no longer hold the support shoe to remain clear of the window frame. The support shoe drags on the window frame and makes window operating difficult. The desired part is no longer listed by Pella.

I would like to replace the entire mechanism held by the two screws pictured.

Do you have a source for this part?

Bob 

Bob - Just fixed this exact thing for my parents. While your rollers are worn (a lot). My opinion is what you really need to replace is the plastic guide that keeps the roller aligned and running parallel with the window frame. A 39-371 should fix it.