You can put
THIS on each wheel and then with a machine key you can put the wheels directly on the output shaft of the toughbox.
The problem is that in most cases you need support on the other side of the shaft in order that it won't get bend, so it will be wiser to get a longer shaft and put a bearing on the end of it, with the bearing inside the chassis and supported.
If you decide to go with hex shaft the you need hex bearing to the end, but not hex bearing on the wheel since you don't really need bearings on the wheels because they are direct driven and putting a bearing will lose it's point so
THIS will work with a hex shaft.
If you need further help you can contact me in mail
ygutman1@gmail.com, i am also from Israel so i probably will be able to help me more then some posts in here...