muffler or spark

Hi, my name is Torben and I am new to the Husaberg crowd! I have a 2003 501 and absolutely think it's a great bike! I do need to find a muffler/spark arrestor for it?? I tried all the usual places( aftermarket companies) and NO one can help......does anyone here know where i can get one? I have...

anyone have any data or opinion as to how restrictive this muffer/spark arrester is? would an after market Big Gun provide any improvement in power or have any thermal bennefits