A new set of N Scale modular bridge components is available at Shapeways.
https://www.shapeways.com/shops/bonevalley?section=N+Concrete+Double+Catenary&s=0
The bridge is based on the Gunpowder and Bush River Amtrak catenary Bridges in Maryland. There are several modular parts to choose from to make the bridge the size you want.
All the parts are available in White Versatile Plastic, which is strong but has a grainy surface texture. The smaller parts are also available in Tan Fine Detail Plastic.
