Where are you staying? If you're staying in a hotel they should be able to give you a glass of cows milk - when we've been in hotels, even just at a wedding reception, we've asked for it at reception or the bar, and it's usually free. It might not be full fat, but this won't matter for a couple of days - and to me would be preferable to/less of a change than switching back to formula.
Or you could buy a pint from a nearby shop and put in the mini fridge in the room if there is one.
I've also seen cartons of milk with a straw in the baby section in Boots - think it's UHT treated so not sure how it tastes, but would be easy to store as no need to refrigerate until open.