Muskett Mufflers in New Zealand make a replica of the G/S muffler.
Fit is good and it is hard to distinguish from the original.
Cost is good too..
IF you go for chrome it will need some tidying up before polishing
The steel is better than original .
Mine is coming up for 20 years old and none of the rust that appeared on the original unit during the warranty period.
Paul Rooney makes a junction box that can be adapted to work with the muffler.
It is designed to work without any second stage .
Comes in stainless and you would need to cut the anoying kink at the back of the headers to get it on as it fits like a GS junction box instead of a G/S junction box.
My bike is slow but the earth is patient.