Need a new animation created

the easy way would be to find the animation you want from one of the many stores selling animation files... most people selling animations at stores include some way to contact then if you want a special order

once you have the animation you may need to convert it to match Mixamo standard [note not a real standard as they keep changing it willy nilly]... for this task I use software call 3Dexchange which is part of the Iclone system but other plugs for Unity or Blender are also around