I have some very old Vintage Reproductions dry transfers, but most of mine are from copies of a drawing. I have no idea where the original image came from, but many years ago I made a master with multiple N scale images, and ran off a few dozen copies. Today, I'd probably go to a highway sign website and get an image.
My signs are either heavy cardstock, with the printed image glued to it, or crossed brass strips, soldered together and to a post, with the paper glued on. For those, I cut the image into individual boards, so it would fit the two brass strips. It's a lot more work, but the brass signs are almost indestructible. However, if they're in a place where you have to reach around them, they may not be the best choice, because they can easily cut an arm...
Either way, the signs are cheap, and exactly the style needed.
