If you only need to replace one specific piece, individual trays are widely available:

This comprehensive set from Walmart includes round, rectangular, heart-shaped, and cupcake pans. It also comes with 60 cupcake liners designed to fit the smaller toy oven dimensions.

An award-winning set available on eBay that features a nonstick finish. It includes four different pan types and 75 liners, making it an excellent choice for a gift.