I may be wrong and stand ready for correction but, there are only 2 sizes of round headlights, 5 3/4 and 7 inch. The bucket may be (would have to be) larger, but they are still considered to be one of those 2 sizes, as they are identified by the size of the light, not the size of the bucket. And of course a 7" beam on a smaller bike would look huge. It would be extremely rare that a manufacturer would deviate from these standard sizes as they outsource their lights and the suppliers provide standardized sizes.
Of course many modern bikes with fairings have flush mount glass, but that's not what we are talking about here.
Many smaller bikes (and older like 60s and 70s) have individualized lighting but they are smaller and more rare. A OEM headlight (just the beam, non the shell) for my CB77 is $75 and is unavailable. Non-standard size. I think a 7" round beam size is the largest standard size out there.
OCICBW