Good luck, Paul!
THEORY
A better option would be to find computer images of the relevant instruments, rescale them to the right size and then make your own decals or print them off on glossy paper and stick them to the model. You can buy transparent water-slide decal paper from several sources on the internet (or so I'm told).
PRACTICAL STUFF
Don't forget that a dial of 4" diameter would rescale to only 1/12" (2mm) @ 1/48 so don't go too mad trying to get exactly the right dial face because you'll never be able to distinguish them once re-sized.
Dave M

Edited By Dave Milbourn on 12/04/2014 12:50:46

Paul
I use a variety of different-diameter sharpened tubes (in my case from an old broken transmitter aerial) to cut discs from self-adhesive vinyl labels, trim strip etc. Silver or pale grey look OK for small instruments. These sharpened tubes are also great for boring clean holes in balsa, ply, styrene etc. Hours of fun!
I also have a rather posh set of laboratory cork borers which do essentially the same job but with far more panache!
Dave M
http://www.rapidonline.com/Education/Cork-Borer-Set-of-6-06-6604

Edited By Dave Milbourn on 12/04/2014 13:50:01