puch maxi, they came with both e50 and ZA50 motor variants, better to search by your motor type than the bike's specific model - mopeds shared many different engines so it's much easier to find parts searching for an e50 than searching for a puch nostalgia or whatever.
that said, you got a maxi - it's the most common moped by a long shot so the above advice is pretty meaningless. you'd be better off still lookin for e50 since all the bottom end stuff is different but the cylinders are all interchangeable. you do want to use a piston that matches the cylinder but again theyre almost all interchangeable between the different e50s and za50s
it's broken down in detail here:
but the TLDR is: it'll run fine on there.