Spezial-Gleitmittel fur Glasschiebedacher.
Special sliding compound for glass sliding roofs.
Comes in 30 ml (1 fl oz) container. Not sure if smaller packages are available as it is very expensive even though it is made in the USA.
Probably best to go to dealer or someone who has a container because 30 ml would last for many lifetimes.
Compound is also good at eliminating plastic noises.