Railroad-Oriented Vendors

Oakridge
Hobbies - O Scale - Offerings include structural components
like beams and girders; building decorations like staircases, shutters,
windows, doors, chimneys, skylights, ladders; textured styrene and plastic
sheets for realistic brick, stone, metal, vinyl, and wood exteriors; dollhouse
furniture including kitchen, bedroom, bathroom, dining room, living room,
and other types of furniture; kits for building entire buildings; dollhouse
wallpaper for interiors; lots of accessories including vending machines,
pool tables, cement mixers, forklifts, musical instruments, playground
equipment; asphalt, concrete, and water-type mats for terrain; ready-made
foliage; and the list could go on. Oakridge has something for every scene,
but don't expect it to be inexpensive.

Valley
Model Trains O Scale - Wide selection from multiple manufacturers.
Take a special look at the Evergreen
Hill Designs detail parts, Model
Tech Studios detail parts and Model
Tech roofing, Plastruct
Inc. rock and stone exterior sheets, Schomberg
Scale Models detail parts.

Search
eBay for "o scale" items - Much of what you will
get will be buildings and railroad cars, but sometimes you will find useful
accessories.