I think there is no point in trying to reproduce the repeaters as they can be obtained from old/new stock BMC/Leyland parts.
As far as the rear indicators are concerned I have a suggestion.
The silicon material that I used and mentioned in another post is readily available under the name 'Silicon Rubber', this can be found in the IN. This material is fantastic when it comes to reproducing very fine detail, such as the inner diffuser surface of the lens.
Have a look at this, and many more, in YouTube.
http://www.youtube.com/watch?v=ADXlUIkdqHcThe lens could be cast, with a very slow setting hardener, using epoxy resin mixed with transparent orange colouring. The slower the setting time the lower the heat produced, resulting in a longer mould life. It may take a bit of experimenting with the colour mix, what the hell NVNG.
Epoxy is unfortunately not all that cheap.
Of course you could always melt down some old orange lenses, but I don't think the mold would like it.
This way you can make an exact reproduction of the original lens, plus the cost would be quite reasonable if more than 20 sets were produced.
I would have no hesitation at having a shot at doing this, the only trouble I have no original to copy, there is not a big enough market on this side of the ditch, plus the high price of shipping from here to the UK, and last but not least, too many irons in the fire.