My son has seen some of his older schoolmates owning this backpack, and now that he is starting primary school he would like to have one.
Backpack has a whistle on the strap / band (not sure about the English term): the whistle is actually a sort of buckle, you can fasten the backpack with it (I think).
If you understood what I'm trying to describe... do you know where can I find it in Basel / Lorrach / Weil am Rhein area?
I've seen these on skiing rucksacks quite a lot, but I don't recall all the brand names. Salomon was one, I'm sure. But these are on proper outdoor/skiing/hiking/climbing kit, so any decent outdoor shop will have them and should be able to order just the buckle/whistle as spare parts, I'd imagine.
I have a Mammut Spindrift Guide with a whistle as part of the chest strap. You an see it if you select the second picture and zoom in on it here . (The whistle is the part which has three semi-circles one above the other).
Exactly, most hiking/climbing/skiing bags have integrated whistles. It's there for safety, not for fun If you can't ask the parents, why don't you take your son to a shop and let him find a backpack he likes? He has to try some on anyway, to make sure it fits.