Here's an idea, but you did not hear about it from me!
Take a straight on side photo of the trailer in question, print it out, lay tracing paper over the print and trace what you need. If you need a pattern any bigger, find an overhead projector, transfer the tracing to a clear piece of acetate, shine the projector on a smooth wall, moving the projector to or away from the wall will change the size of the image. When I first started making signs in 1987, this is how all sign patterns were made, now we use computers and do very little by hand.
Good Luck and be careful, copyright laws are for real!!