My experience is so old it is probably of little value. In the 70's through the mid 80's when I worked at an AC dealer, we replaced those pumps. I don't know if that was considered the most cost effective route at the time, or if someone in management decided those pumps were not rebuildable.
There are, within a couple hours either side of me, repair shops which specialize in all types of hydraulics. That's where I would go with something like this.