The older G3's are a bit different than most bikes in the front end, it seems.
The forks only being 24" long means pretty much everything is too long if you decide to swap the whole front end. The closest I found was a CB100-125 that have 27" forks. I'm not sure what the fork spacing on those bikes are though?
I think you know I decided to just go with cast wheels from a 125CBR but I can understand this look isn't for everyone... The axle is bigger on the CBR but plenty of meat in the G3 forks to bore them out.
Physically the wheel is as narrow as the G3 but I haven't even got to the point of mocking it up to know if the disc is going to be an issue...
Alternatively, I know a fella working on a KE 100 that has swapped the whole front end with a KX100... Upside down forks and disk, but I personally don't like the look of 8" of fork above the triple clamp to keep the ride height proper. I'm wondering if there is a relatively cheap way to shorten forks? If so, it might be cheaper to just buy the whole front end of a bike???
Lots of guys with small Honda's here, maybe someone can help you with measurements for determining a good candidate?