I made some. You can get self adhesive ink-jet vinyl (try www.overlander.co.uk ), I'm sure there will be suppliers in most countries. I then scanned the logo in from the box, tidied it up on the computer and printed it to the required size. I have done this for both the YS roundal and the engine-specific logos.

One thing - the ink is not fuel proof so you also need to get some clear vinyl and stick that over the top.

It makes a nice neat job that whilst up close you can see is not professional, stand back and you wouldn't know any different.