As far as I can see in the exploded views, both the MT4 and the ST1 came stoch with 8mm stub axles, like almost every 1:8th scale car I know of.
In the pictures I see a standard sub axle with some flat spots ground on them, done by the owner.
The MT4 comes with these axles, not in stock, but you should get the idea:
http://www.dollarhobbyz.com/collecti...shaft-assembly
The FG square hubs are like these, the part number depends on the width of the hub:
https://rc-car-online.de/en/products...5mm-steel.html
The other pieces look the be just a peace of brass pipe, with a ID of 8mm, and a bolt that fits in the axle, you should be able to get that in your local hardware store, or at a machine shop?
I think I am misunderstanding you, my English is not that good, sorry.