I am away from home quite a bit with work, but I always make sure I either take enough to last me or that I am close enough to a supermarket/Boots/Superdrug etc to be able to pick some bottles up - seems to work OK.
TBH I find it much easier than when I was on SW as there's none of this "can't eat this with this and can't eat that with that" - I just stick to calorie counted ready meals (much nicer than they used to be), a big bag of salad and my shakes and I'm good to go