M.A.
Hi D.,
I also like a hooded sweatshirt and pants, you can find pink felt and cut it out into circles (grey bigger than pink and then fold inside out, fill with a little filler)for ears and some hot glued for the tummy. I would say grey or even white would make a cute mouse! A painted face will make all the difference. If it is for a girl, a large hodded sweatshirt with white tights can work too!
If you want something more elaborate, I woudl suggest you go to a store like Jo Ann's or Michaels and ask in the fabric section, they usually have fake fur that is not very expensive and they can suggest what to do, they may even have some patterns if you are good at putting it together.
Hope it helps!