Hi,
My 'new' A7 plunger wiring harness was virtually all brown and black wires plus a purple or two with no diagram - very helpful! However, with an ammeter it didn't take too long to work out what did what. I've now found a diagram that sort of describes where the wires go (will scan and supply if needed). But if all you need is the yellow and green wire from dynamo then Autosparks will make a braided length up while you wait for a couple of quid - black and white fleck braided.
They make harnesses for many classic bikes and sell to the trade who we know and use - I think mine originated from Auotsparks according to them!
http://www.autosparks.co.uk/They're located just outside Nottingham, literally 10 minutes form J25 M1 - and when I've called in they've also been most helpful and very cost effective; cheaper than Vehilce Wiring Products by quite a bit.
In 15 minutes they'd made up two new sections for me with an extra earth wire added in - bargin price!
And they're nice people! Oh they supply the new thin high amperage wire if wishing to slip a new wire in here and there.
Cheers
RoadRunner