You could, get the sidelights out of an old pair of main lights, then you have to carefully drill a hole for them and see if you can get the bulb to stay in.
TBH, I've seen premade angel eye inner lamps about, and that is a whole lot easier than the process of drilling into it and trying to get the bulb to stay.
At any rate, you'll need to mess with some wires to get them to work.
Here is a set of inner angel eyes, but not sure about the company...