At short haul at BA we get £10 paid into our wages when we start to account for a float that we might need during any fight.
We have travelex offices that change up money commission free, they also give us as many floats as we need in return for cash or money of our dinners or other cards. Normally open at most reasonable hours of the day.
Purser is also advised to carry a float at all times as are main crew "just in case"