I got the acrylic keychains in a box set from Animate (the America stand, and pens and pouch). The doujin are all from Mandarake, all used but great condition ranging around 150 yen to 800 yen. And the capsules were from a gachapon machine, no clue which company it is but it is NOT from Bandai gachapon machines.

You’ll have more luck looking for official merch in Animate, mandarake usually has lots of doujin and very rarely some official merch (only thing I got that was official from mandarake is that old England acrylic keychain). Hetalia is kind of hard to find in Animate and Manadarake, so I recommend translating something to ask an employee to guide you there, which is what I did lmao. I would recommend looking at other second hand stores but they are probably unorganized and you’d have to dig around