there is a kit that allows you to make your own decals with a normal inkjet type printer but I am sorry I cant remember who makes it. As for having them made for you could try to contact http://www.railgraphicsdecals.com/ they do prototype or custom decals. You being able to draft them up yourself would help. Good luck
Several companies, including Testors and Micro Mark, offer decal sheets available in clear or white. They have different papaper for ink jets or laser printers. The problem is that you can’t print white lettering, and light colors don’t work real well, either, since the ink is not opaque enough to block out the background color.
You can do white lettering using the white paper if you match the background color of the car or loco and use white lettering on the color or black background of your software. Unless your background color is black, it will be tough to match.