No retail store stocks vintage Cushman motorized scooters as the company stopped making them in 1965. However, they can be obtained from a variety of websites such as Ebay, CushmanForSale.com, ClassicCars.com and the Smart Car Guide (SCG).
While Cushman scooters can be purchased, they are both rare and expensive. All of the sellers listed above are auction style sites, with product availability constantly in flux. Parts can be hard to come by as well, though the above sites also deal in these. One popular alternative is to purchase parts and then construct a scooter yourself, though this is still expensive and very time consuming.