I have cut down new air hoses (cut off the crimped on fittings and replaced them with old fittings from decrepit D&RGW narrow gauge air hoses.) for a few narrow gauge cars. Cutting can be accomplished with a chop saw if you don't mind the stench of burning rubber. If you have a scrap yard that cuts up railcars in your area they will usually give you the air hoses from cars that they are cutting up and a surprising number of cars make their last trip with brand new air hoses. I suppose this would work for any older car if you have the old style fittings. Also, for narrow gauge cars that will be used, New York Airbrake makes a new hose that is the exact same length as teh old D&RGW narrow gauge hoses.
Jason Midyette