PR and BPI have the roll-crimpers, and the swager is pretty simple, if a little kluge-y.
I had a local machine shop turn one out of a piece of sch80. It was two-ended. I clamped it in a vice and swaged with a rubber hammer.
- 'A' took the shelf down from .95± to .935-ish
- 'B' was the more critical operation, as it shaped the radius at the rim, and pulled the last .008? out.
Those measurement are from memory, but the shop built it from a print I found on the 'net.
8ga heads are all brass, and they are not that hard to shape.
If you call Tom Armbrust, he might have a swaging rig you could borrow & copy. My die is ... 'elsewhere' (apparently permanently), or you could have it.
Bob