http://www.flyncycle.com/acatalog/CBR_600_87-90.html
Just found this site, prices from $170 to $304 for a slip on, and they have a mini.

 

That is pretty slick. I had only seen the original on eBay before. I like my V&H, but it is nice to know we have a little bit of a more variety in exhaust choices, especially one with a shorty. Note that with those kits you need to get the mid-pipe and mounting hardware seperately.