Try looking on DVD rental stores or libraries. Sometimes they have older movies like A Cinderella Story with Brandy. Also, check out some lesser-known streaming services; you might get lucky there.
Some online movie rental services like Amazon Prime Video or Google Play Movies could have it. You could also check your local cable TV's on-demand section.
You might be able to find it on popular streaming platforms like Netflix or Hulu. Just do a search on those sites.