Want to buy a specific schoolbag from Japan as a souvenir, can someone give me some advice?

I want to buy a specific schoolbag from Japan as a souvenir, and I tried searching on Yahoo Japan and Amazon Japan, but I couldn't find the exact same bag, which was frustrating for me as a perfectionist. So I wanted to ask other people, especially Japanese people, if they have any search suggestions, like keywords or something. Does anybody here have any suggestions? I personally think this might be difficult for non-Japanese people.the picture of schoolbag