Hey in france when on these small stock or small 50s or small 70cc builds (not like polinis and Malossi's ) lots of people tend to use what we call a Turkish pipe, its a little longer than oem, but fits fine and it's not got any baffles so its a little noisy, but it works great especially in the mid range to the top of a litlle 70cc. U c them in Turkey with one of these and a 15mm carb going 120kmh down masive hills sucked in behind semi trucks on stock av10s!
heres a video of an airsal 45 stock av7 bottom end and variator with a "Turkish" exhaust.
If u order one from Turkey theyre about $5-$10.
But otherwise Ebay one guy sells em with some markup.