Hey Zsolan, I have loaded the image files I have created as download links to the following page. https://nameless-designer.itch.io/heroes-of-adventure
I used The Game Crafter to print the boxes using one of the standard box sizes (9.5" x 11.5-12") from memory. It was simply a case of selecting the box and uploading the template. However, I did run into a snag that I had to prove ownership of the game before they would print my order (in case they thought I was trying to rip off someone else's IP) so I'm not sure whether they will allow you to print one for yourself. I'm loathe to setup a page to allow people to 'buy these' (even if is at cost) as that creates the impression that I am selling something and I'm not. In addition, for low volume printing they are fairly expensive as a warning.
Hope that helps.