I have a set of comstars from a 78 cb400 twin. The rear has a drum brake, the front has a disk. I'm not certain of the exact sizes at the moment, though I know the rear is 18" diameter. It fits 3.5x18 tires, as I recall, though nearly every one Ive ever seen has been refitted with 4.00X18s.
I'd be willing to sell my comstars, if they will work for you. $25 each, plus shipping from Wyoming. Let me know if you are interested and I can snap some pics.