I'm noticing in these photos that a lot of the more conservative "middle aged man" suits are cut very similar to modern classic fit suits sold today. The length of the vest and the rise of the trousers are the most obvious traits to me.
Kabel, not sure which scans you're referring to, but i know that small Japanese companies like Django Atour and Adjustable Costume have made early 20s inspired jackets and suits in the recent past, but i don't know what is currently available from either, and they're not easy to order from due to their sites being in Japanese.
SJC is offering a late teens-early 20s style suit soon, but i don't think it has buttoning pockets or all around belt.
Who or what is SJC?
SJC is an apparel (and soon to be lifestyle) brand