Casters may wear out over time, and we understand the need to replace them. Because of this, they are available as replacement parts and we will gladly sell you new ones. Prices are specific to each model but a set of two will generally run around $16.65, including shipping.
The casters should not be switched out for different ones, third party or otherwise. The included casters are the appropriate size for leveling in hand truck mode, when all wheels/casters are in use. We carefully test our products for use as intended and any variation from this would void the warranty.