You could look at the Inglewood parking shuttles.  You pay both for parking and for each individual taking a shuttle.  But there appears to be capacity available even for events that have a very short lead time.
https://inglewoodparkgo.com/

A less expensive option seems to be the [Gardena 7x Bus line][1].  It runs for games and picks up from the Harbor Gateway transit Center ($3 parking on game days).   I couldn't find anything recent, but a 2018 [Reddit thread][2] said that the facility did not fill up on game days. 


  [1]: https://ridegtrans.com/line/7x/
  [2]: https://www.reddit.com/r/Chargers/comments/a4gd09/does_the_harbor_gateway_transit_center_parking/