you can use 4*lr44 button cell batteries. use scotch tape to keep them together and aluminum foil to fill up the extra space.
as for the cannonet, its a Varta 625 battery you re looking for. you can find it, sim lim tower basement battery shop, or ruby photo(saw tehre, but not sure if they still stock) but you can also get a LR44 and put card boar around to make it fit in the hole.