-

-

Do you have access to a lathe?

Would;
2 of dia of hub face ex x 12mm int x 10mm spacers
1 of 12mm stainless rod
2 of 12mm washered nuts
A 12mm die
and a file work?
Thread ends of rod, file a flat on the the 12 and 6 o’clock on each end, pop through hub, pop on a spacer each side, fit nuts. Ride away. I’d give it a go, but No you go first.

https://www.bilcastors.co.uk/product/th12x2x10/ something like this? then a 10mm axle and track nuts

-

-

-

-