Try a search for titanium racks and Cuben fiber panniers, but that will likely result in zero to few hits. Generally speaking there are no ultra-lightweight rack/pannier options. Not sure if I have seen any silnylon panniers, but I know some panniers weigh much less than others (e.g., Ortlieb backrollers at 4 lbs 5.5 oz vs. Nashbar waterproof rear panniers that have been modified to make them more robust at 3 lbs 2.5 oz). Often lighter weight panniers won't be as robust and if your bike takes a tumble, panniers will get scraped.

P.S. Maybe you have identified a market niche; are you entrepreneurial?

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Here's an option to reduce weight -- don't use racks:

http://www.carouseldesignworks.com/main.html
http://www.epicdesignsalaska.com