Here are some suppliers that I have found very useful. The search for specialty items for a geodesic dome has been exhausting, so I hope to pass along my knowledge and make your quest easier.
Grower's Supply - a wide variety of greenhouse film, polycarbonate and other coverings plus everything else for professional greenhouses and growing. Excellent customer service in my experience.
ACF Greenhouses - Geared more to the hobbyist, a good source for top-quality construction materials and supplies with competitive pricing.
Harvest Moon Hydroponics - There is a local branch in our beautiful Lehigh Valley which I have. Impressively stocked with all your hydro needs plus environmental controls and fertilizers.