I have never heard of the Cosmo shifter before you posted the link. Schnell, B&M and OEM shifters is what most have gone with with the B&M being the most popular on this forum. As X51 stated above B&M made the Porsche shirt (sport) shifter for the 996.
I went with the B&M and loved it. Eric at BumperPlugs.com sells the B&M shifter for $199, plus he is a Rennlist site sponsor.