My aluminum wheel adaptor gizmos are held onto the axle with some period Mini-Auto axle spacers:
The polished chassis with the permanently installed wheel gizmos:
For wheel inserts I want to go for this look:
I'm used Monogram Chaparral 2D model kit wheels. To turn them down to size I used my hobby lathe and held the wheel with a "pot chuck":
A little gold paint and a "black wash" to finish them off:
I looked into using an 0-80 stainless steel hex nut to mimic a center lock but I wasn't happy with it.