Second hand designer watch

Hihi i’m going to osaka to study and ive never been there before, my boss is asking me to bring back a second hand designer watch (rolex etc?) and that japan is famous for having the best second hand watches(?)

I’m just wondering where the best place would be to get one for relatively cheap, or even just good quality.

I know nothing about watches so how can i tell if they’re good enough or the main brand?

thank you in advance :))

by eloheleren