If they're already made, I'm not really sure. I know some people use super strong magnets sewn onto/in their clothing or to a support structure underneath it to hold up props like that. But they usually also embed the twin magnet in the prop during construction.
Scarlet Witch (with Quicksilver), Dagger (with Cloak, 2013 Ultimate editions), Stahma Tarr
Chosen, In Planning:
Red (with Subject Unknown), Evie & Jacob (Lady and Duke outfits)
Ravager, Braum (with Illaoi)