Bring your own stash!
You don't need all of this, but it did make me feel at home in Holland and Paris where it was very hard/impossible to get a good cup of coffee.
If you are traveling light I would recommend a Hario ceramic burr hand grinder. Perfect for grinding beans on the road. It has an adjustable grind setting which is crucial. The downside is it's takes some elbow grease to get things going. So it's not great for brewing a big pot or having a coffee party.
Also a single cup brewer/filters of some kind (v60, Melita, Aeropress). I like the V60 I have a glass version, but it also comes in ceramic. The V shape and detachable handle is great for packing. Most hotels have a coffee pot so you could heat your water that way, but all the hotels in London conveniently came with a hot water pot for tea. Don't forget the COFFEE!
Stop by Everyman and if you don't want to schlep a grinder we can help you out, but remember that as soon as coffee is ground it starts to loose it's flavor. It starts to "DE-GAS" and after a few days will not even bloom when you brew it. :( So getting a grinder and adding a step is worth it.