Here's The Next Best Thing If You Don't Have An American Flag For Your National Anthem

It's actually prohibited by the US Flag Code:

"The flag should not be used as 'wearing apparel, bedding, or drapery'"

The flag can be on apparel, just not used as apparel, as in, taking a real flag and making a dress out of it.
Otherwise, US soldiers would be in violation for having a flag on their uniforms

Cypresstiger, also from the Flaf Code:

"The flag should not be used as part of a costume or athletic uniform, except that a flag patch may be used on the uniform of military personnel, firefighters, police officers, and members of patriotic organizations."