In looking aeound at sticker sites, I think the lettering will need to be bigger - maybe the whole width...
I'll check around for the cut vinyl. I prefer to put stickers on glass and white usually stands out better. But to apply to the camper siding, black would stand out better.
One site I looked at had a 50 piece minimum but the price per was good.
I saw another site that could do printed stickers like the euro oval ones for double the price but no minimum.
I'll check around some more as I have time.