The narrower width would seem to indicate it is an early version of the Climax - reversing light mounted on the bunker. The later version - reversing light on the cab roof - has a similar 4 pocket, multi height, but wider. Not sure what to suggest. Looks like Bachmann are out of both. You could try to modify one of these 16mm scale 3D Printed Parts, the Ruston 4 pocket buffer beam. Max
In my link n pin days I did use pop rivets being lazy. But made the links out of brass strip drilling holes for the pins each end. I did find that a variety of differing lengths of links were required for differing stock. Rather than spend lots on the vehicle couplings I used U shaped channel again with drilled holes for the pins secured to wagons with small ba screws. For some of my small LGB fleet at the time I cut off buffers, sacrilege but as most had been obtained cheepish I was not that concerned. For a time all of my garden trains had compatible coupling. However I binned them in the end as I found that derailments tended to derail the complete train. likely running a bit too fast.
