[lugerholsterrepair]

Bill, You have to concentrate on era's when talking rivets. They are relatively common on many WW1 leather items, not so much as repairs but items made with them. They were so common on leather items I think they were used extensively for repairs because that's what Saddlers had and since it was quick and easy...that's what they used.
In the WW2 era there were different rivets. They changed from the solid rivet to the hollow rivet. I say changed but you will find the use of the solid rivet still into the mid 40's.
Then there is the Norwegian conversion rivet. I have seen these mostly in hard nickle steel and also aluminum. Generally a larger rivet than some of the German types. These might have come from the U.S. like the G.I. belt hangers but that's speculative.
I have restitched hundreds of belt loops and it is relatively quick and easy to do. The holes are already there, they have to be cleaned out and ...restitched properly takes a short while. I have to suppose for the unskilled Saddler a rivet would be faster.
I don't see that many belt loops fixed with rivets but I have seen some.

Jerry Burney