I did an epic google looking for a supplier of the correct sort of material in the UK last night, with no luck. Plenty in the USA of course...
I expect if it's available as round bar stock, it's just a matter of learning to machine it. But if it's cast, well, that's where it gets a bit more difficult!
Skateboard wheels eh? I'd have thought the common ones are far to hard being upwards of 90A or so, and I reckon we'd be after 70A - 80A depending how hard you want your rear end (ooer missus!)
"Two very small men cutting steps in the roof of the world"