Welcome.
The good thing about your Manco is it uses very common
parts, not manufacturer specific
parts like Honda, Kawasaki, Yamaha, etc.
In a word, industrial.
Other than the bodywork, most
parts you can find from companies like Grainger, and even the local hardware store.
https://www.grainger.com/content/general-catalog
The best part is the engine, because you can easily replace it with something like a new, inexpensive one from Harbor Freight. It would probably be an upgrade too, yours likely still having a side valve engine.
Here's a YouTube video of someone who put a newer engine in. It's just one example. There are others.
https://www.youtube.com/watch?v=HPSQqTmbKEg