The silencer is basically a wire mesh tube with insulating material wrapped around it. If you take out the bolts at the base of the silencer and slide the core out, you can unwrap the insulation from the wire mesh tube.
It sounds like the wire mesh tube is either broken or corroded and you likely cannot buy it separately. You may have to buy a complete new silencer.
After you get the problem fixed, to prevent this from happening again and to keep the bike running and sounding its best, you need to keep the packing fresh by changing the insulation every so often . :cool: