you can pretty much use any puch or minarelli pipe.
the only thing you have to watch out for is large headers because morini exhaust ports are kinda small. for fitting a puch exhaust like the bullet or estoril you have to grind in the mounting holes a bit beacause puchs are wider apart than that of morinis.
Angelo can get good stuff, but exchange rate from Italy is kinda rediculous so it gets a bit pricey. i got a circuit style minarelli pipe from him a while back. its nice but you could get a bit more out of something like an estoril. but, i'm not sure how a pipe like the estoril would work on a non kitted bike.