You can always check around on that one website that starts with E and ends with bay. Decals turn up there. Everyone here uses gil_m to get reproductions. You can
@gil_m somehow on this site to contact him (I'm not great with tech stuff). You can also go to his website
http://www.thecycleshed.co.uk/frontdoor.html, or find him on Facebook under retrodecals, or email
sales@retrodecals.co.uk
I also found this link, while searching for gil_m,
http://www.velocals.com/servlet/the-Roc ... Categories .
To me, keeping a bike original vs. buying new parts comes down to aesthetics and feel. If the old parts work and you like the way they look and feel then use it as is until something breaks or wears out. I think most people around here would advise you to keep everything as it is in this instance, since, as you say, it's original and in amazing condition. To break that up by getting some new parts would be slightly against the ethos of this site (not to put words in anyone's mouth). That said, if the parts were not original and/or in shite condition, then most folks on here would say - do what you want with it. Going period correct but lighter can get expensive. If you think you'd use the bike more or for some reason have more fun on it ("feel") with new parts, and you like the look of new parts on old bikes, then go ahead and switch out the old stuff. Just know, you might run into fitment issues with new parts and an old bike frame (you can update a lot, though).
Good luck!