Purchase small plastic wheels for model cars at eBay.com or HobbyInc.com. These sites feature a wide variety of plastic wheels and other parts and accessories for model cars.
At eBay.com, type "model car wheels" or keywords related to a specific type of wheels in the search box at the top of the main page, and then click the Search button to display a listing. Refine your search by clicking Automotive Toy Model and Kit Parts beneath the Categories heading near the top left of the page; as of November 2015, this search yields about 250 listings, most of them model car wheels. Some products are for specific models, while others are generic products mountable on various models. Click a listing to display detailed information or to make a purchase.
At HobbyInc.com, click the Parts/Accessories button beneath the Plastic Models heading near the top of the main page, and then click the Vehicle Tire and Wheel button in the Plastic Model Parts and Accessories section. As of November 2015, this listing includes more than 120 products, including wheels for Pegasus, AMT, Aoshima and Meng models. Click the Add to Cart button to purchase the product or click the Pre-Order button for out-of-stock products.