Where can I find obsolete tool parts for Milwaukee drills?
My drill is a Heavy-Duty 3/8" Drill, Model No.: 0228-1 and I need a replacement for the Reversing Spindle, Part No.: 38-50-5370.
It might not be possible to find a commercial store that still stocks obsolete parts, particularly those of Milwaukee drills. I suggest that you find a used drill off of eBay with the same model number as your drill then remove the parts.
Try e-bay or Craig's list.