The blue-and-white kimono (actually called "nemaki") are easy to find. Just go to any department store and ask for their kimono department. You'll find the "nemaki" in different sizes and fabric designs wrapped in plastic on the shelves.

Some designs are considered masculine and some are considered feminine, so tell the sales clerk who the nemaki is for.

Tokyo is full of stationery stores. As a certified origami klutz who can make Japanese people double up in laughter at her attempts to fold a crane, I've never looked for origami paper. However, the famous stationery store on the Ginza is called Itoya, and it has a sign in English. If they don't have origami paper, they undoubtedly know where to get it.