I dont know specifically where in Osaka, But Nagoya (a smaller and less touristy location) had a tv shop that had figurines and what not ... And I think Tokyuu Hands had a floor with that kinda thing in it as well.
Basically just visit a really big department store - There are three Tokyu Hands stores in Osaka alone and a simple google search will give you maps (even in english)... best store ever definately check it out!