German police patch trade

Hello everyone! Me and my husband will be in Osaka for our honeymoon next week. My husband is a German police officer. In Europe it is common practice for policemen to trade the police patches (coat of arms) of their departments with each other. My husband already has gathered a big collection of patches that way. He would be overjoyed to add a japanese patch to his collection but we heard that it is uncommon in Japan to trade them since everyone only has one patch.
Since I know how happy he would be I want to try it with this post anyway.

Has anyone got any sort of japanese police patch that he would like to trade against a German patch? Or do you know anyone who maybe does? I would be very happy to heat from you and meet up when we are in Osaka next week. Thank you for reading this regardless and have a lovely day!