I replaced both of mine a few years back because one of them was dead.
I bought some cheap meters (from eBay (China), I believe) and transplanted them into the original housings.
I remember the bodies (coils) were slightly larger so I had to hack away at the original plastic housings.
I believe the bottom pieces of plastic were the only ones I left, they temporarily located the meters while I rebuilt the rest of the housings around them.
Unfortunately, I don't have pics of the process, just some from when I posted it for sale.
It was very delicate work and definitely not an easy job but they did turn out pretty nice.
The only difference was that they were orange instead of white.
I tried a to paint them but believe it or not, the paint was too heavy and they would barely move so I had to remove it and just left them orange.
I ended up selling it and took pics of the meters in action because I noted that they were not the originals.
My phone has these under the November 2019 file which seems about right.
I did consider if buying random meters would work correctly but it was a shot that I was willing to take.
Since you have your donor meters in hand, you can temporarily wire them up to the 5259 and see if they respond correctly before attempting the transplant.
The bodies of the meters are held in by friction so if yours are the same size, they may slide right in (you'd have to be really lucky for that to happen).
If they're too big, you'll have to do what I did, if too small, you might have to wedge and/or glue them into the housings.
I bought my 5259 with the dead meter not knowing what I was in for and wouldn't buy another one with this problem after my experience.
The only way I'd do this job again would be if one of my current boxes had a meter die.
