I have never tried this but you could and lets us know if it works out. Make a large three dimensional shape from cardboard or styrafoam.Cover it with some releasing agent - vasoline or just liquid detergent. Cover the shape with 4 or 5 layers of paper strips dipped in flour paste , or what ever you use. When it is dry cut it  in half, rejoin the sides and cover with several more layers of papier mache. Finish it off witha layer of gesso, or latex house paint, and then paint it with acrylics and seal with water based polyuerothane.

Good luck.

Can I suggest you use a balloon as your mould? Blow one up to the size of the body,vasline it, then cover with lots of layers of papier mache.  You can just pierce it with a pin, and you won't even hear the pop.  Add legs made from cut-off toilet roll insides, and a tail from a pipe cleaner, or paper rope.  I'm not sure about the head, but that will need to be made from a cardboard mould I think.  Add ears, and cover the whole lot with more layers.

Find a bung or cork for the bottom, draw around it, and cut a hole in the bottom to fit.  Cut a hole in the top for your money - measure your widest coin to get the size right.  Smooth the edges of the holes, and cover with a few more layers.  I would paint mine pink, with some nice 1970s flowers, and possibly a message or rhyme to remind myself that the money saved is for a rainy day, not just for taking out when I've forgotten to go to the bank!

Sue