A obi ita is a stiff piece worn over the kimono (Japanese dress) and under the obi (belt) in front. This helps keep the wide obi from wrinkling when you bend or sit down. Many anime fans / kon fans / cosplayers find wearing a kimono is fun. Obi itas are not items you can easily find here in the US though. After looking at eBay for one, I figured, "heck! its just a stiff piece of something with ties around it. Surely I can make one..."

Thus started the brief search for materials around my house. Cardboard bent too easily, and at odd stiff angles, while some things didn't bend at all. I really didn't have anything suitable laying about.
I was out shopping and happend upon these thin cutting mats in the kitchen section of my local Bed Bath & Beyond. They were only about $6 for a pack of four. How could I resist?
So I took it home and measured against my sash (my obi hadn't come in the mail yet). It turned out if I split it in half lenghtwise it would cover almost my whole obi width, and wrap just around the front half of my waist!
So this is what it looked like nearly completed:
So I got two obi ita out of one cutting mat, and 3 other cutting mats to use in the kitchen for about $6 (I had the ribbon already, so it was free). You could make a set of eight obi ita for under $10 if you had to buy some ribbon at the craft store.
good luck and enjoy wearing your kimono! Here's me in mine: