Is it possible to resize an image of 4 Kb to 725 bytes with some filter without loosing the form

Deal all,

I would like to create a Face image to insert in my mail message, the 
first step is to resize my image to 48x48 pixels.
My starting image is this:
http://i250.photobucket.com/albums/gg274/gialloporpora/foxkeh2.png

of 4400 bytes
I need to transform it in an image of at most 725 bytes:
http://quimby.gnus.org/circus/face/

If I resize it  using ImageMagik I obtain an image, 48x48, of 2200 bytes 
that is too big.

Somebody know some idea to reduce the size of the file?
If possible, I would like to use only two colors (monochrome but not 
black and white).

Thanks
Sandro