You can find the manual for free to get part numbers for the kart.
However, many of the parts the kart uses are generic/standard parts.
Stuff that you would probably have to buy that are Manco are:
Steering wheel, spindles, possibly sprocket if the old one is worn
Generic stuff you could buy is
Bearings, brakes, torque converter, engine, seat (hopefully), etc .
Looks like an old subaru ex17 is. On there. If you get a new engine, the predator 212cc engine would be a good replacement which you can buy at harbor freight. It is cost prohibitive to fix any subaru small engine as the gas tank costs $80 and carbeurator is $99. A brand new predator 212cc engine is $99.