well you can just write on the bills until you get a stamp
the benefits of a stamp are it is much neater & it is much faster.
to get a stamp made you can look in the yellow pages under rubber stamps. there are probably shops that make rubber stamps.. or else you can go to office depot or a place simular.
we also have a user in saskatoon who makes stamps, but i would guess shipping & handleing alone would pay for a stamp.