Hi Jim
It depends if you want to keep it original with regard to the throttle cable. If you don't mind the look of a newer replacement then something like GA spares CAC7434
https://www.gaspares.com.au/products/CAC7434?Muffler something like this
https://www.gaspares.com.au/products/MUF1851?A few photos would help, as some used a different throttle cable
Perhaps someone could recommend a trustworthy sharpener in NSW