A baja 4-1 extractor, then there's the plain collector style or the merged collector for ultimate performance if the engine is better than stock in regards to cam/heads etc.
But it depends on your barwork (rear cage) whether they fit.
This one is the cheaper plain collector type, with the quite loud hotdog for muffler, there is also a quiet muffler available, and also there is an option with or without your std heaterbox's
http://www.thesamba.com/vw/classifieds/detail.php?id=729232
And this page has more merged extractors, used for higher performance engines, tube diameter is another consideration depending on performance level.
http://www.appletreeauto.com/raw-single-exhaust-c-492.html