Partsplanet.it offers Termignoni replicas. Sil Moto makes a decent spaghetti system. There's not much else being made new.
These are the Partsplanet Termi copies (though when I bought these they weren't advertised as copies...)
I ended up making my own brackets to mount them but otherwise they've worked fine. I'm not sure if the issues I had were because of the parts, or my bike. The original system was tweaked when the bike fell over in an earlier life so the headers may have been bent too.