It sucks having to delete some superstars just to get newer ones. Especially if you're downloading specific ones for Universe mode. Maybe next years game we can get more
Best way to find them would be to search the specific username for each superstar and download straight there. Or you can search the name under the My Hashtag in the search and hover each superstar until you see the creator name
Unfortunately, the last WWE2k game for PS3 was 2K17. Im not sure if the community is still active enough there for newer creations. I would suggest pausing the screen on a specific superstar and creating your favorite ones by hand. It'll take you some time but I know you'll be happy you did it