Funny you should ask...
I have been doing detail work in the lens department myself. Oddly, on my 1974 USA, I have only the rear red side markers and not the amber fronts I have seen on other cars. I went ahead and jumped on the ebay listing for new red rears...$48.99 ea. Pricey yes, but not near as bad as the price I paid for new euro type front turn signal lenses, and was worried about future availability. (my old stuff is, well, old and frazzled) The turn signal lenses are for sure a nice aesthetic improvement. I needed to shave the bulb reflectors about 1/4 inch to make fit. I could post some photos if there is interest.