Hey Ted,
I also have a 68 L72 and had to replace the driver side arm rest a few years ago for my parchment interior. These are a lot harder to find than it seems like they should be. The only one I found at the time was from Classic Industries and they're only available in black. (Great if you have a black interior). I had to dye mine parchment. Be careful to specify 2-door. The majority of what they offer are for 4-doors for some reason. https://www.classicindustries.com/product/all-years/chevrolet/impala/parts/7755939.html