Military M-65 Leather Jacket

The coat I bought was the M-65, beautiful & well made. I bought it with the following; thick black, XXXL, measured to me, thinsulate lining & rustic silver zipper.
I have only one issue; the zipper is undersized, it should be a larger grade zipper for a heavy coat. As it is, it's the grade of zipper on a pair of jeans.