If I'm understanding what you're aiming to do, then one rough and ready way if you don't need too many wheels and have a lathe and mill to hand may be to fabricate some webbed inserts/overlays as follows:
- machine a length of brass round in the lathe to the diameter of the webbed piece to be inserted between the wheel tyres
- drill the centre of the round to take the axle
- remove brass round from lathe and mill one of more grooves (as many and as wide as required) across the centre line of the machined and drilled end. The grooves will hold brass flat of suitable size to simulate the pressed bits
- put the round back in the lathe and part off as thin as you can
- repeat as required
- to finish the inserts, fix short lengths of brass flat into the grooves with glue or solder
A bit long winded but just a thought