Originally Posted by
lagers
My measurements of the inner diameter varied from 33.5mm to 33.8mm. I measured the width while I was at it which was 70mm. I'm not sure if the outer diameter matters at all, but it was roughly 42.8mm.
33.5-33.8mm ID is very close to the ID of a standard BSA bottom bracket thread. This, combined with the slight chamfer on each side of your bottom bracket shell, makes it seem like the ideal candidate for a bottom bracket like this:
https://www.ebay.com/itm/373738703299
They are sold under the brand names "Sunlite" and "YST" here in the USA. I bet you could find one in Japan!
I used one for a couple years on my commuting bike. It had to be quite tightly screwed together, or would come loose, but a little threadlocking compound helped with this.
Edit: I see [MENTION=45088]nlerner[/MENTION] already mentioned this option.
I do think the Velo Orange is probably higher quality.