Sounds just like the 79 puch maxi I bought last month. It too needed a new rear tire and tube as well as the fuel petcock, air filter and a rear brake cable. I paid $125.00 for it and am very pleased with it. I was able to get all of the parts I needed for it from the Moped warehouse in new jersey. they are at 201-819-9050 if your in new jersey or they have a toll free number on their webiste if you are not.
Good luck with it and enjoy. By the way mine is the onespeed model.