I actually heard recently that the at the end of the Special Olympics big event, they have a big party for the kids and the volunteers often provide prom dresses and such for them.

It was all secondhand from someone who was assisting volunteers there, but maybe it's a place to look into if you're interested?

Call around to some of the local high schools. Hillcrest I know for sure might take them-I think they have a dress closet for prom. If they don’t take them directly they will know where to point you.

-Edited for spelling.

Shine Inc.
https://www.shineinc.shop/

Ambassadors for children has a prom closet for foster children.

Yes! The Cinderella Closet at Hillcrest. A friend is the teacher that runs it.

I know Hillcrest accepts donations