Here's a copy of an explanation by CrackShot in 2015 and is very applicable to your project.
"My inclination is to use a period process.I have drilled the hole very snug and simply twisted it tightly into the hole. A length of drill rod was slid into the powder hole to drive and bend the wire over from inside the horn. I had a firm and watertight attachment - as judged at Dixon's. There was no need for any "faux hide glue" or "modern pine pitch resin" to be mixed, stained and pressed into the hole.If the center powder hole is not straight for easy access - as is so commonly the case, I have used a bit of brass rod with a slight bend to it in driving the staple ends over to lock them down from inside. Very specialized custom made tool - rivals my horn neck cutting gauge for complexity...
A side note, (which can be seen in the photos) I do not hang the horn by the wire bail, but rather tie the strap around the neck and through the wire bail which simply serves to hold the strap in its proper place on the neck. The wire is then not working nearly as hard. I have been told that this was correct and it makes sense. If you look at originals, most of the wires are pretty thin and it is doubtful that these held the weight of full horns."
You can use the 3/32 steel rods commonly find on the web or use welding wire that can be found in Lowes in bales for a few bucks that will last a lifetime. In addition, please don't twist the staple. It looks cool but the old timers knew what would happen to your strap after must rubbing against the sharp edges of the twists.
Hope this helps.
