How to find guest play opportunities

Does anyone have tips on how to search for guest play opportunities at the high school soccer level?

My son is a center back playing in ECRL. He wants to play in college at the D3 level. He’s been to a number of ID camps and has been getting positive feedback from coaches. But they need to see him play and they don’t tend to go to the tournaments his ECRL team plays in. We’re trying to figure out how we could get him exposure at these tournaments as a guest player on a team that does play in them.

Any suggestions would be greatly appreciated!