FMF P/N's for Service Honda 2008 KX450F/500AF. Since Service Honda no longer makes the aluminum frame conversions FMF may be willing to sell you what you need. However they may still be honoring the original agreement with A.J. Might be worth a try?
FMF pipe P/N 122000
FMF Powercore 2 silencer P/N 122001
FMF "Q" silencer (spark arrestor) P/N 122002