Assuming the spacing between the bearings is workable, what I’d do is find/make/have someone else make some sleeves that have an 8mm id and 10mm OD. Pretty basic machining.
The other option is to make some spacers that adapt a 608 bearing to whatever size the bearing seats are. Also pretty basic machining.
Of course, another option is to just buy some trucks with 10mm axles…
I’d suggest looking around locally to see if there’s any kind of machine shop. Come up with an accurately dimensioned drawing, and take it to them. I’d guess an hour or two, at whatever hourly rate they charge.
There are small-run prototype machining services available online, but for one-off (or in this case, four-off) parts, it’s fairly expensive.
Well if you look up a 6200 bearings dimensions they are 10mm x 9mm x 30mm. Which means you are after a 8mm x 9mm x 30mm bearing, 2mm thicker than your current ones, but you can’t fill that space with a ball bearing without increasing the width of the bearing right? Because the balls are spheres. So assuming it existed, which I don’t think it does, the only size of bearing that would work would be 8 X 11 X 30. 2mm too wide.
