Sven,
Marcus and I have posted epic amounts of research on this subject in the previous posts he kindly linked for you. His info is worth a lot. He knows more about this subject (& has shared it !) than many Porsche Tech Departments.
I am acknowledging that because you seem to have lost interest.
Here is a helpful article on the subject from Pelican:
Porsche 911 Carrera Gbox Second Gear Shift Detent Installation - 996 (1998-2005) - 997 (2005-2012) - Pelican Parts Technical Article
$200:
http://www.ebay.com/itm/PORSCHE-TRANSMISSION-996-or-BOXSTER-DETENT-NEW-FIXES-2ND-GEAR-Pop-Out-/151517255422?hash=item234721d6fe:m:m1FHVX0IfU9prwM oY_p80Eg&vxp=mtr
Cheaper from Erik Johnson:
http://www.renntrack.com/forums/showthread.php?1278-Detent-DIY