Sources for Explosions and Other Assets in USDZ format?

Does anyone know where I can find quality assets in USDZ format? For Unity and Unreal Engine, I just use the built-in asset stores. There seem to be a number of third-party 3D model stores like Laughing Squid, but they tend not to have models in USD format.

In particular, I'm looking for some nice-looking explosions for a RealityKit-based visionOS game I'm writing. Some nice boulders would also be useful.

Thanks in advance!

Sources for Explosions and Other Assets in USDZ format?
 
 
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