Exterior door trim moulding is available from The Home Depot, Lowe's and Royal Building Products, as of 2015. Additional sources for door trim include Menards and Vintage Hardware and Lighting.
The Home Depot features moulding made from a variety of materials including composite, medium density fiberboard, polystyrene and wood. The moulding types include back band, base, block and brick.
Lowe's features door casing trim kits, doorjamb kits and door jams. Royal Building Products sells exterior trim and moulding for doors, windows and roofs. Vintage Hardware and Lighting features a Victorian-style door moulding trim that comes unfinished and ready to paint or stain. Menards sells trim for a variety of household doors and windows.