If you ever go to Harajuku, I highly recommend entering the basement level of the Laforet department building, where a lot of the big brand stores exist, and asking them!

They're incredibly friendly staff who work at Lolita and Goth brand stores, and they're happy to have a conversation with you (out of politeness, you should probably go in with the intention to buy something before starting this conversation, though). Ask them where people go, where you can meet and see other Lolita.

You could even mention that Lolita around the world talk about Harajuku Bridge on a Sunday and see if they know what you mean.

I would've thought if anyone knows where Lolita are found, it would be the shop employees (they're working in a lolita clothing store for a reason, after all!)