Here are a few of my favorite necessities for travel days and for use in other countries.
The first link I provided is the adapter that I currently use and it works for most outlets worldwide, as it has different settings for EU, UK, and AUS/USA outlets. It has 4 USB ports as well as a Type-C port, so you can connect and charge all of your electronics at once. I actually use this in my room even when I am not traveling since it has a US mode and I can keep all of my electronics plugged into the same outlet. Here is a similar one.
Carry-on dual purpose neck pillow
Personally, I do not find neck pillows comfortable and never use them to sleep while flying. However, this neck pillow is worth it because of its special makeup. My dad is my biggest supporter and actually sent this to me last year because it is such a cool travel hack- the concept is to fill the inside of the neck pillow with extra clothes so that you can bring more than what fits in your suitcase. So while I don’t actually sleep with it, the airlines don’t need to know that:)
Here is the article from Travel + Leisure detailing the neck pillow that I currently have.
I bought this for the first time at the Savannah/ Hilton Head International Airport before my first trans-Atlantic flight in 2021 and now swear by it. As someone who is generally unable to fall asleep on flights, this combination of melatonin and GABA seems to help me tremendously. Of course there are many other similar products, so finding something that works for you can be a godsend during long travel days.