Jeff-
Do you mean you want to install 'modern' belts, but are hoping to find them in the 'turquoise-y' color? You can get belts to retrofit in just about any color- do some googling, maybe throw in 'hot-rod' into the search. I know when I was looking for new belts for my 122 (I got tired of explaining how the 'staplegun' latch worked to passengers, nevermind the lack of retraction!) I came up with a bunch of places offering them. The problem for 'the Bird' was that nothing that I found had a receptacle support that kept it more-or-less 'at hand' (they either came with too-long plastic sleeves or just with a short, floppy strap). I ended up getting the black Skandix belts as they have a rigid cable that keeps the receptacle where I want it. But for back-seats you'll have to use something with a short floppy strap anyway, so your options are greater.

I can't remember all the places I bookmarked when I was looking, but you can start somewhere like here: http://www.gotbelts.com/

I do remember the prices varied wildly!