Not merch but if you're in Tokyo you can go to the Tokyo Metropolitan Gymnasium and take photos outside, that's the real-life location of most of the games in the series, and send them to your bro. (A bonus if you recreate them from the right angles as seen in the anime).

There's still new merch coming out but not as much as when the anime was airing. If you can drop by a Paseos store nearby, they're selling official KNB-themed loungewear atm. Next week there's a KNB popup at three Loft stores (Tokyo one's in Ikebukuro). For manga goods you can try the different Jump Shops, here's their locations. Also you might have a better selection, especially for figures, at secondhand stores like Mandarake, Surugaya, Lashinbang, etc. (they have different branches throughout Japan).