Amazon.com: Delkin Devices DDCD-R-SA/25 SPINDLE Retail Cakebox Spindle - 25 Pack: Home Audio & Theater
they hold about exactly (if not a tiny bit more) than a gd-r. im surprised no one has thought to use these for the dreamcast yet. first time i ehard about them was today but they have apparently been out for a long time.
Double-density compact disc - Wikipedia
it says only one writer came out but im pretty sure a driver can be written (if not aleady exists) since most burners can handle bluray and dvd, which could have more than one layer.