Read your post and started looking for myself since I have a moonroof as well...
nothing...
Is yours torn or damaged? If it is leaking and the seal looks good, there was a thread a month or so back about the drain lines being clogged. The OP cleaned out the drain lines and all was well.
If it's in good shape, clean it and keep it coated with some armorall or something.
... or try a boneyard...