Real - or counterfeit - England megatone dampers, Norton S-pipes and Dunstall Db dampers are quite expensive. Chinese reference is pretty cheap.
But part of that Chinese offer is so muted that your classic cafe racer under construction - and who doesn't build a cafe racer at the moment? - it can cause breathlessness.
Above a certain speed the Chinese throttle the engine block in its own exhaust gases.
Briefly close that option with your supplier and notify him by e-mail that he will get his things back in case of suffocation.
Because if it looks fantastic, but it doesn't work, then 50% simply misses its goal on a cafe racer
Incidentally, Peters Classic Bike Parts, for example, supplies Dunstall and Megaton replicas made in England. They are only slightly more expensive. And do what you expect from them.