I read somewhere on Dreamcast-Talk.com that one possible, cheap and permanently (at least as long as people drive in the rain and the dark) available remedy is headlight scratch/film remover. Just like a clear plastic get less clear over time, the theory is so does the optical disc lenses.
My Dreamcast does all the memory issues right, but stopped reading the disc. I saw a video that if the disc spins full when it's held "almost closed" that reseating the plastic will fix it for a while. I tried that and it didn't work. Besides It wasn't running while holding the lid mostly down.
Since you should try the least drastic likely-to-fix-it step, should headlight defogger & scratch filler be that next, least drastic step? Or is there a cheaper, less drastic step for someone who is kind of klutzy and the most they've done by themselves was clean Atari 2600 and Bally Astrocade potentiometers and installed an alternate cable for a joystick 9-pin Flashback adapter on the Intellivision 1, and thinks he can install an NES Blinking Light Win, but never tried. I don't have a soldering gun, any electrical testing equipment, or knowledge on how to use either.
By the way, I do not need a car headlight size, I need a CD lens size. I don't need to spend a fortune for Headlight quantities, when CD Lens quantities is all I need.