I still haven't found the official size of the ISS pizza box and a search on the WEB doesn't help:
"30 miles deep and 30 miles long around the space station": https://www.vice.com/en_us/article/3dkpyn/international-space-station-dodge-space-junk
"two kilometers above and below the station and 25 kilometers cross-track and down-track": https://arstechnica.com/science/2013/07/how-nasa-steers-the-international-space-station-around-space-junk/
"±25 km in the direction of motion, ±25 km perpendicular to the direction of motion, and ±0.5 km radially from the ISS as it flies in orbit": https://books.google.de/books?id=9mseNE1wkLMC&pg=PA145&lpg=PA145#v=onepage&q&f=false
"0.75 kilometers above and below the station and 25 kilometers on each side": https://www.universetoday.com/92571/iss-will-do-manuever-friday-to-avoid-collision-with-satellite-debris/
Is there any official size?
Pizza box: a safety region around the ISS. Please, see the 3rd link page 145 for an authoritative definition, which, in fact, answers my question (from that preview I didn't realize it was published by NASA).