Black Bear Construction Company is selling materials packs for their trestle and bridge jigs. My O Scale pack included enough material to build a five leg trestle, more than six inches tall with full lattice and bracing supports. The materials packs are available in Z through O scales and do not include their acrylic jigs or details. These can be purchased separately or as a kit through Black Bear Construction Company's web site.
Although the packs are intended to be used with their jigs, these are also great for those of you who like to scratchbuild and design your own bridges.