Buffel - and fortunately that's it, there aren't any contextual spellings like other German words. That is exactly what it looks like on the side of the vehicle.
As for font, I'd say that it is probably letterd with a 3/4" brush but painted with a little flair.
After studying it a little it looks about this:
There aren't any decal sets out there that I can find, either on Squadron or GM. So I would say the best idea would be to print it yourself. You can use the drawing I made or make your own, and scale it so the entire word is about half the width of the engine louvers (something easy to scale from in that picture) Just get some expert's choice decal film and print it on your printer's best setting. (do not, DO NOT use the Testor decal making kit. It is absolute garbage)
Or, if you don't feel adventurous, you can have it custom made.