Pick up a used series 3 harness for not much money and strip out whatever colours you need ... works for me.
That's smart. Best answer in this thread. Too late for me.
*blushes*
But seriously, if you are inclined to get a used harness, before you buy, strip back some of the binding tape and check that the pvc coating of the wires hasn't hardened ... coz by now ie ~45 years later, a lot of that stuff is brittle. Another benefit, is that you also score the moulded connectors.