So I've been wearing size 10 gauges for a while and I for the life of me can not find any Astro Boy gauges I might just have to get some custom made :/
That's a cute name for them though I've been searching for Astro ones for awhile now and yeah that's actually exactly how you do it the smallest you usually start out is size 16. I'm on size 12 I don't know why I said 10 in my first post. I want to get up to a 10 and that's it. The bigger the gauge the smaller the size number,
I would try Etsy.com and see if you can find some. I found Megaman cufflinks on there as well as some other very rare and unique treasures! You can also try and commission some from numerous craftsman that are on the site for a reasonable price.
If you can find the Japanese word for it, try Googling for it in Japanese. If such jewelry is available there they might have it in a Tetsuwan Atomu style.