I believe your original window in the door setup may have had a roller shade between the inner panel and the outer one, with a tab which held it closed for privacy. At least that was the system used on a couple of mid 80's AS that I have seen and the 310 motorhome I owned. The inner panel was trimmed out with a vinyl slip on molding I believe. So, yours may have been missing the roller shade and that is why it looked unfinished.
The photo you show is a recent door window system, and looks like the one on my new FC 20'. It is an obscure gray tinted glass with no shade. I am not at home right now so can't tell you just how it fits into the door, but it is a very different window from the old ones used in the 80's. So, I don't think it is a simple trim piece that you can use to create the same look.