Kurt, I think the answer is, as far as we know, nobody has made a pattern - or if they have, they haven't made it available.
But I think what you are really looking for isn't the pattern as much as a replacement piece of glass. A couple of us do grab parts from various ambulances we see in junkyards. I buy etched window glass when I see it, though I don't have anything '59-'64.
If you tell us what year (since they are indeed different each year) and what side you're looking for, perhaps someone else here actually has an intact etched glass they'd be willing to sell.