This was a one off from FMF to Sean.
We asked for more, including his Woods Works pipe...
Sorry, they won't make more.
However... If you know someone with a tig welder and some minor fabrication skills you can take just about any 250F silencer and adapt it to fit your KX500 which is what FMF did.
I'll be doing that on my KTX500E build... But more on that later

If bikes are for kids I'll never grow up.