If you ask around at pharmacies or medical clinics in your area, you can get
a powdered version of pedialyte.  It isn't very common here, but it is used
for rehydration therapy for children in developing nations.  It lasts a
couple o f years if it isn't mixed.  If you check around, you should be able
to get some.  Also, it's a lot easier to store.
[Posted in FML issue 1909]