I recently went through this for my 2018 Micro Lite 21DS. I was able to (barely) read the manufacturer off the other lenses and look the manufacturer up via Google. My manufacture was Optronics, and their website was:
Optronics International > PRODUCTS > LED Lighting > LED Marker/Clearance > Products. I was then able to visually find a match, get a part number, and search the internet for replacements which I found. Kinda a pain, but it worked for me.