Just had a little search and cant really see anywhere where you can buy it separately.I fitted my old exhaust without it though, just put loads of paste on the 2 ends and clamp tight with the olive clamp.
http://www.kamracing.co.uk/index.php...e-fitment.html
Yeah its quite loud but not over the top. I've got the straight through s/s centre section with decat and no silencer. Gets very raspy over 3000rpm and pops and bangs quite a lot. That's on a vts so not sure if will be same on a vtr