Because I :heart: Lian Li I did a little looking around.
The only two places i know of that you might contact are Xoxide.com and crazypc.com.
Xoxide comes close with windows for the 1000 & 2000 but not what your looking for.
Both carry a full range of LL gear.
You might be looking at sending them your side cover or you could have a sheet metal shop cut the side cover for you. Then install the window of your choice that you've purchased.
Hope someone else can be of more help.
...Galvanized