[Caymancouver]

I've ordered the same thing for my roof rods. Only one of mine is broken at this point but I will replace both.

The entire metal rod and plastic end is available from Porsche but not just the plastic end joint. The end joints shown in the ebay listing above are easy to install just by unscrewing the broken plastic joint and screwing the new ones on the same number of turns. Then snap the cap onto the metal ball.

Don't be tempted to buy metal end sockets (although they are available). The plastic ones are designed to break under stress so that the motor is protected from damage. (FYI the thing that creates the stress is if something restricts the top from opening or closing properly... often it can happen if the latch isn't fully released before operating the electric switch.)