Well, my plan is to more or less replicate the striping that is already on my trailer-- I thought if I got it made on a white background (mine's a white trailer) about 2 inches wider than the existing, it would cover all sins.
There's a tab for custom vinyl trailer signs. That's where I started. I also had on online chat with a customer service guy who was very helpful.
Now I'm going to go dig out my drawings and get this project moving again!
Actually, if my memory serves me, I found a couple of places that do just vinyl stripes... all my notes are in the office, I'm afraid. But if you google vehicle striping you will come up with some stuff.