It's better if you learn the metric ETRTO size for next time you need to shop for stuff. I would guess almost every mainstream manufacturer will give metric specifications, because ETRTO is a more precise measurement of compatibility to 1 millimeter. There are 25.4mm in 1 inch. When sizes are given in inches, you won't be able to tell how close that last fraction of an inch is to the next whole inch, unless you know the archaic relationship of the inch width standard to it's diameter.
https://www.schwalbe.com/en/groessenbezeichnung
Tubes are easy to find in Europe. Schwalbe makes them in almost every size and there are giant internet retailers who stock them all, like bike24. And they really do arrive in 1-2 days when you order before 1pm (depending on how far you are located from their warehouse).