Indonesian "mud" coffee works fine.
If coffee beans are ground sufficiently fine, you can just put some together with near-boiling water, stir a bit, wait 3-5 minutes and all of the grounds will sink to the bottom.
They really do, if the coffee is ground sufficiently fine.
You just need a cup and the hot water to pour into it. I do this every morning, no need for any equipment beyond your coffee cup and whatever you boil water in.
There will be "mud" at the bottom; either skip the the last few sips if you are squeamish, or when you are at the last quarter of the cup just be aware when you notice a little graininess.
See WikiHow's How to Make Indonesian Kopi Tobruk
Kopi tobruk is coffee prepared in utter simplicity. Indonesian supermarkets sell a wide selection of pre-ground specialty coffees, but your preferred brand of regular grind will do just as well. Sometimes referred to as “mud coffee,” it is one of the most common forms of coffee available in Indonesia. When in Indonesia, knowing how to make your own coffee kopi tobruk is the better alternative to drinking the local instant 3-1 coffees which are sweet or too sweet, or to buying expensive coffee at the fancy coffee shops. Also, it is not uncommon to find a container of ground coffee at the breakfast table of your Indonesian hostel or resort. That's for making kopi tobruk and not for making instant coffee.
Where I live I can buy the finely ground Kapal Api at any Indonesian grocery store. If there's not one around you, just experiment with grinding enough beans for your trip finely and bringing in a plastic bag.
How fine? Very fine. Google "kopi bubuk".