The stock silencer works well and is relatively durable. Maybe you just run with it until "you use it up". These silencers are used in canada, but not here in the U.S. as standard equipment (we need spark arrestors). I don't here of any issues with them being damaged easily.
I know of the following silencers made specifically for the GasGas...
FMF Power Core
FMF Turbine Core (spark arrested)
Doma
DEP
Pro-Circuit (not currently listed on their website).
Messico
The other option is to find a used stock silencer and shorten it. But as I said, if it were me I would "use up" the stock silencer before worrying about it.
As a sidenote - varying the length of the silencer does change the performance characteristics. Going with a long silencer, besides making it quieter, provides enhanced top end power. "Shorty" silencers are used to enchance bottom end response.
jeff
