A local sign maker/graphics place working in vinyl will be able to make them up, though they might need another van to take digital photos of to do it. If your shadows are very visible they might do.
Again if the shadows are fully visible it may be possible to use those as a template around which they put some thin tape with a sharp wire inside it. Then they cover the area with the appropriate colour of viynl/sticky backed plastic and pull the wire out thus cutting the plastic to shape. I had mine completely redone that way a couple or years ago. It was fairly expensive though.
If you could get new ones made or buy them from Autotrail, which I'd expect to be very expensive, you'd need to be pretty skilled to apply them correctly. I'd say that's not a DIY job having put plenty of very simple sign writing on trucks I can say that it's an art and easily mucked up. Though there are a few tricks to it, even so your job is complicated and probably expensive.
Many of those sign places will make complete sets of livery for machinery, tractors and that kind of stuff at a fraction of the cost of buying from a main dealer.
I believe I saw an ad. some years ago from such a company making livery for motorhomes. Maybe try Google.