Being a person who, you might say, has been around the block a bit, here are some items that I really like -
https://www.amazon.com/Anker-PowerCore-Ultra-Portable-VoltageBoost-Technology/dp/B00Z9QVE4Q
https://www.amazon.com/Anker-Charger-PowerPort-iPhone-Galaxy/dp/B00P936188
https://www.amazon.com/Anker-SoundCore-Playtime-Bluetooth-Portable/dp/B016XTADG2
Anker is basically bullet-proof, so just use them and not worry. I believe that all their products can handle 120/240. It’s easy to find plug-adapters on the web, just search ‘Czech Plug’
Obviously be sure to buy a good number of cords, and of the right type.
The battery liberates you from having to find ‘charging ports’ for at least a full day, and one that size is usually enough for 2 people for a full day.
The speaker is optional, and there are smaller ones, it just depends on how much you want to carry, but Bluetooth speakers are great, compared to what you typically get in a phone or similar device.
The power brick that I show is their larger one, it will basically run/charge everything you have, and all at the same time [other than most laptops]. They do have a smaller one with 4 outputs, which is what I typically travel with, since it’s lighter. But be sure to have an extension cord, if needed for the brick. If you do have a basic, single-output, brick, it’s not a bad idea to bring that too, as a backup.
Also watch out for grounding and polarization [one prong bigger than the other] on US cords. It’s overkill in our great society due to fire chiefs having too much political influence [that’s for another thread], and can keep adapters from otherwise working. In my case, I grind-off the polarization and also cut off the stub on extension cords that prevents the use of a 3-prong plug with a 2-prong extension cord [try plugging one in and you’ll see]...so far, I’ve survived.
Have fun and enjoy the really cheap prices there as well as being away from the ‘social experiments’ going on to the west of that country!
FWIW, the polarization and “3rd prong” are there to prevent electrocution if your appliance has an insulation failure inside. Double insulated appliances lack the third prong, and provide safety with, tada, double insulation instead of safety grounding.