I would not worry about this. I would call Mike and Ed and talk to them about what you are looking for. Getting on a high quality connected team is as important as anything IMO. They both run multiple teams and they are always looking to add extra talent. If they don’t have a spot they can refer you to another team.
As a fill in on any team for one event you will be at the bottom of the rotation and I would not expect too much playing time given this scenario. I would question any team looking to add a fill in committing much playing time as they are either a) A new or a daddy ball team who will not attract much attention at the event. b) Charlatan looking to take your money.
Others include, Okeiki, Play Vista Orioles, Trombly Braves, and the Pasadena Saints. ABD of course has a ton of teams, but will cost you.
Good luck!