ideally I was thinking the style that was a clear lense with a black "interior" that only showed red when they were lit up, but anything less red would be interesting to try. I appreciate you guys at least confirming my Google skills aren't total junk though. maybe I'll try to build some if I can find a cheap junkyard pair to take apart.
I went looking for tail lights back when I did my projector "upgrade". I couldn't find anything different than normal other than some stock Euro spec ones with the rear fog light on like the 20th page of results. That was a couple years ago though.
Just looked and nothing available other than LED taillights like the 2011+ vans have, and the standard earlier tails.
I'd go with a junkyard pair and experiment. You can mix clear and black paint to spray them just like nightshades, or wrap them in smoked vinyl (easily removeable if you don't like it). If you could get an early 5th gen set of tails, the lenses are pretty flat (just one curve) so might be easier to heat up some clear acrylic sheet to form your own outer lens from. Cut to shape after bending/cooling and fit. Then you can paint the inside of the light and use colored LED bulbs and add red reflectors where needed (by law, rear and side). Light output for back-up lights may suffer, so you could plan to add auxilliary back-up lights somewhere else.
At least this is a project that can be done indoors over the winter months!