As suggested in the video link (https://www.youtube.com/watch?v=WJRh43flvQ8) passive speakers could be the solution. They usually come with basic audio wires and you would have to attach these to a 3.5mm audio jack yourself. They may also be called Cabinet or Bookshelf Loudspeaker.
Impedance of these speakers is very important to avoid creating an electrical short. The suggestion is 16 ohm with 8 ohm possibly also working, but it's not without risk from my understanding.
The speakers brand in that video is called: Apart and they have different product lines available: e.g. SDX / SDI / SDQ / Ovo
Another similar example would be JBL Control, but that appears to only have a 4 Ohm resistor, making it a bit of a risky choice I think. Another one is Audioengine P4 and you'll find plenty in any audio-hardware selling shop.
The main problem (for me) with these is the price and size. They are more higher end products, not exactly small (understandably so if you are looking for high quality sound). Naturally, they also don't come with a 3.5 mm audio jack.
I also found these: Pyle Home PCB4BK 200W 4 inch Mini Cube, which are not as pricy, have 8 Ohm impedance and good reviews. There are a bunch of those cube shaped speakers available.
Obviously, you can't use any of these with a digital audio output - well, you would have to put a FiiO converter in between, which will need power and make this sort of pointless.
Most out of the box solutions on the smaller side are called something like External Loudspeaker or Computer / Tablet / Laptop Portable Speaker. Strangely, these will generally require being charged and/or come USB/AC powered. Examples are: Logitech S150, XMI X-Mini II, Frisby FS-210NU, Earise AL-101, AmazonBasics Computer Speakers, etc.
Obviously, there are plenty of Bluetooth speakers available as well. Bose SoundLink Mini is one with decent sound that also has an analogue line-in, but these need recharging every 8 hours of use. They are mobile, though and you can use them anywhere around the house.
Ok, back to the passive speakers. They won't come with that 3.5mm audio jack, because people expect you to put an amplifier in front of them. If you want to do it yourself, there is something on instructables: http://www.instructables.com/id/How-to-wire-a-speaker-to-35mm-jack/
Now, this won't always work as the results will highly depend on how much power your Audio-Out provides. People tried this with a raspberry Pi and there it didn't exactly work. A monitor Audio-Out may give you better results, though.