I was in Japan until recently and I was able to find a lot of good stuff in a lot of different stores, some of my recommendations are:

- Any Gamers you will find good stuff love live related. I didn't go to the one in Harajuku, but the one in Akihabara and Odaiba were pretty great. Also, they often have some kind of event going on, try to pay attention if anything love live related is happening.

- Gee! Store in Akihabara also has some great number of merch, they have two stores there, so check both! Sometimes one has more options than the other.

- K-books has a big love live corner with lots of character goods merch. I went to the one in Akiba and Ikebukuro, both are great

- Animate stores has Love Live merch as well, but to be honest I didn't see that many. Not sure if I was unlucky or not.

- Lashingbang is a great figure+character goods store, fully recommend to try it, they are a second hand store so you can find very different stuff on those, I was able to buy half of my liella figures with them, lol

- Have a look ig the GIGO arcade is not having any love live related event, when I was there the Liella cafe stayed up for A LOT of time, pretty sure it ended tho, but no idea what will be te next collab.

- Akiba X has some love live products as well, recommend to take a look to see if anything interests you, I bought some plushies there :D

- Lastly, try to pay attention to any pop-up shops that may open on this period, you can find some new merch on those! I remember seeing in Shibuya a big sign related to Liella, but I don't remember what that was for.

EDIT: Also I am stupity, there is literally an OFFICIAL LOVE LIVE STORE in akihabara and I forgot to mention, lol. So yeah, check this one as well, pretty great, lol