This stuff that's recommended by the TSBs really worked well in quelling those nasty sunroof creaks, I picked some up at a car-detailer place:

3M™ Silicone Lubricant Plus (Wet Type), 08877 - A high solids, high viscosity aerosol lubricant designed for lubricating moving parts, eliminating squeaks caused by friction; protecting against rust and corrosion; sealing out moisture; preserving plastics, rubber, leather; etc.

I called the SF BMW dealer inquiring about the Gummi product (that's suppose to work really well too) and he says it costs $50! Apparently they're not going to carry that soon either, and the other product they wanted to sell me was going to be $130 for a chap stick-size tube

BMW - The Ultimate Rip-Off Artists

 

So did you eventually get it from one of the dealers?

I tried to ask performancenissanparts to get that part for me, but they never responded....