Aye Richard,
My first suggestion would be to contact 'David Silver Honda Spares':
David_Silver_XBR_spares I cannot see anything in their list, but would suggest a telephone call or email could bear fruit.
Alternatively, I would suggest that you contact 'Classic Transfers':
Classic_Transfers Whilst they do not show a stock of transfers for Honda models, I know that they create their transfers in house from their own artwork, that is excellent. The tank transfers on my Ducati are water-slide transfers from them.
Thirdly, if you have a good example of the transfer that you want to reproduce, take it along to a vehicle wrapping company. If they are worth their salt, they will be able to scan your example, clean up the image and then be able to print off as many copies as you require of the transfer in vinyl that you can then get applied after painting the tank and then over lacquered to protect it and the paint.
If you have problems locating a good vehicle wrapper, I could take your image to my local wrapper. They produce film wraps for Stagecoach buses, to one off vinyl transfers for my Ducati side covers, from my sketch layout, while I waited!

They then printed off 6 copies for £24 and kept the image on their database in case I needed more copies.
I hope this helps, Bill