Good sources for N-scale include IMEX (on line search, several distributors...) and the old "LIberty Falls" series (now available at cruizn4sailz.com), These are solid resin-cast, ready to plant. Also, of course, Walthers has many, many by Pola and others, some simply N-scale versions of the same stuff that's in HO.
Railsider
Railsider