This is what my 13 year old son and I made over Xmas.
Angle iron $30.00 (Steel merchant)
Cast alloy 110kg rate castors 6 x $8.50 (Bunnings)
Paint I had lying around.
Time building something with my son "priceless"
Sits about 15mm of the ground and can use either the side stand or centre stand.
Rear ramp removed for easier loading
Front ramp pushes down and lifts the front castors of the ground 5mm and stops trolley moving forward when taking off the centre stand.
Cheers
Dave