Try these boys..
www.protocraft.com
I've gotten some O scale decals from them and they were quite good.
This website has links to a wide variety of O scale structures, parts and details including some of the names mentioned above such as the Bar Mills roof vents.
http://valleymodeltrains.com/website/oscale.html
Also check out what Crow River has.
The old Selley line of white metal castings has some O scale stuff that Bowser continues to list. That includes some roof vents. It is easy to forget the Selley line these days but back when I started that is where the young modeler on a budget tended to look first!
http://www.bowserorders.com/.sc/ms/cat/O%20Bowser--Selley
Dave Nelson
Also check out Scale City Designs online. They bought everything for the O scale parts line of Kiel-Line, who in turn, got them when Walthers quit manufacturing their O scale freight and passenger line. SCD is adding things from those great manufacturers all the time. (I've bought Fox Patent freight trucks and a dandy set of castings, designed by Walthers, for heavyweight observation car railings.) Prices are reasonable and service is excellent.
Deano
Rusty Stumps has some O scale cast resin pieces. Berkshire Valley Models, Crow River Products, Bar Mills, Hamm River Model Products, and once in a while some "unknown manufacturer" pieces appear on E-Bay. Walthers has HO vents that might be passable for O scale.
Mark B.
Walthers and Modeltrainstuff both list O scale items. The Walthers O catalog used to have detail parts in it.
Also check with the folks at Classic Toy Trains, they do more with O scale.
Good luck,
Richard
Folks,
Can anyone assist in locating O scale parts....roof vents, side cage vents, L shaped vents, saw dust burners, and smoke stacks, jacks, and chimneys......or any other O scale detail parts either for roof top or anything do do with O scale structures.
Many thanks,
HZ