If it's stock, go check Suzuki's web site and see what they say about the machine and it's specs. It may state Ti exhaust, if it is. Do some searching on the motorcycle in magazine articles too.
Stick a magnet to it. If it sticks, it's mild. If not, it's stainless or Ti. If the header's off the bike, pick it up. If it's nice and light, it's Ti. If it's fairly heavy, and the magnet doesn't stick, it's stainless.
For exhaust parts - tubing, bends, all sorts of stuff, check out
SPD. They carry everything you could need to make an exhaust system. (I just ordered stuff to finish my exhaust from them yesterday).