They’ve been known to be the one to get for quite a while so aren’t as easy to get as they used to be, I’ve seen them fitted to several BMW’s also.
Pretty much any GSXR/TL/SV pipe is better than the stock one though. I run a single TL1000 pipe and have experimented with a GSXR600 pipe. Here’s some of my experiences: https://www.adventureridingnz.co.nz/forums/topic/random-adventure-riding-pics/page/3/#post-10992