Pokémon GO

[TeridaxXD001]

Hey I'm the author of this package - I don't remember that the assets get cleared from the device when they are no longer used.
Since the assets get downloaded from the servers on-the-fly, your best chance would be to sniff your network traffic and grab the download URLs from the servers by hand. IIRC, these URLs use hash tickets, but they should be valid for ~1 hour from any device.
Your next problem is, that the assets are likely encrypted. I don't remember if they used an actual encryption (search /r/pokemongodev) or if they were just compressed UnityFS files.

Edit: Might a good place to research: Link

What's the best way to sniff traffic? I've used Fiddler before, but you need to install a certificate to whatever device you're sniffing and the game won't work with one.