Hey Allan,
I don't know of such a decal sheet, but you can check on scalemates.com.
Although you can cut the roundels out with an Olfa circle cutter from a Tamiya or AK yellow Kabuki masking sheet, it takes about 10 minutes. You can cut out the red and blue >> marks very easily with a ruler and scalpel. You can mask easily the red-white-blue markings on rudder and paint them.
Alternatively, you can draw these in a vector graphics program, such as Adobe Illustrator, and cut them out with a plotter (e.g. Silhouette) from masking sheet.
The numbers 6, the squadron mark and the factory number 32517 on the rudder can be drawn in a vector graphics program as well. Alternatively, you can ask a graphic designer to do it for you.
Then find a printing company that prints on decal sheets using a digital printer. Here it's important to get a printer that can print white (the cheaper ones can't). Aviattic and Lukgraph decal sheets are made this way, there's nothing special about it, it's been standard technology for many years.
If the printer company doesn't have a decal sheet you can buy one, several manufacturers make them. There are also white and blue carrier paper.
All in all, it's a relatively simple task, easily done in-house. It's how I make markings to my kits. I mask the larger and simpler shapes, and draw the small and complex graphics, then print them on decal sheet. Here in Hungary, where I live, one of the hobby shops does this kind of decal printing, they have the machine and a quality decal sheet. Presumably there is such a company where you live.
