Shell,
Magnesium rubs can also be bought through chemist - my sister is a footy trainer and when the guys come of the field with a cramp this is what they get - along with a lecture re dehydration as this can also make symptoms worse.
I rarely have cramps after increasing my fluid uptake and i rub the cream on if i get a cramp and days that i feel dehydrated.
They are awful and i woke screaming with one several months ago, i hope this helps for you as well as it did for me.
BTW i thought that you shouldnt have quinine when you are pg - i could be completely wrong here thou