As Zspripe suggested:
Try here:
Petersen Brothers Plastics
2929 N. Pulaski Rd Chicago, IL 60641
Ask for Color Cast Acrylic. They come in transparent or opaque.
http://petersenplastics.com/materials/acrylics-and-polycarbonate-sheet/
petersons plastics product is very close to my needed color. I can also pick it up it is pretty local to me. i saw a post about foil and a shower curtain idea i had. the foil causes waves and the curtain acts as the water. you glue the foil down and staple the curtain under the thicker cardboard. i saw this at a swap meet last weekend it is pretty convincing except the color is off from my other areas. i know most of the curtain colors out there and the colors are off from what i have and this would not be a realistic option. by the way at this swap meet i picked up 2 steel bottle cars and the earlier thimble cars for 18 bucks plus i need to weather them with slop. i can see that not everyone is looking at them as a guaranteed dollar sign at a earlier swap meet someone with a used one wanted 38 dollars and the roling stock was cashed and couplers plus cracks on the plastic.