Sounds like the exhaust system you want is the stock CB550F set up.
I don't think they are available from Honda, anymore. Maybe David Silver Spares still has some. See FAQ.
Used ones may come up for sale periodically.
I'm hoarding mine.

However, you will likely have to change the right foot peg, brake arm and kick start lever from and F model, too. And, make some sort of muffler hanger bracket, as well.
Cheers,