You could try checking dedicated PS3 save-sharing communities or trophy-hunting forums, as that's usually where endgame saves are shared. Make sure the save matches your game's region, otherwise it may not work correctly.
Since you're on a Super Slim with OFW, using a save resigner such as KG Save Resigner is generally the right approach for making another player's save compatible with your PSN account. Keep in mind that some games lock certain progress or trophies in ways that prevent them from unlocking simply by loading someone else's save.
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