Buying yukata (a washable cotton kimono) can be difficult if you are outside of Japan and can't read Japanese well enough to use a service like Noppin or Rakuten. It can be even harder if you are taller than 5'3" or have a chest or hip measurement larger than, say, 34". So, most of us. The solution, of course, is to get a custom-made yukata.
But do you want to sew one yourself? You could. There are quite a few books on the subject (mostly only in Japanese, but a few tutorials in English online). They have lots of photos to follow, and most of the pieces are rectangular... but that can be time-consuming and difficult if you're a beginner. I'm still working on my chuya obi in my spare time, and it's only halfway done... 30 labour hours later.
Or you could just order a custom-made work from a professional kimono seamstress. KimonoPoncho is such a store, run by Tanaka Yukiko. She also sells lots and lots of kimono-making supplies, so if you are making your own and want proper things, check her out!
These yukata are reasonably priced, especially for a custom-tailoured item. I frequently see yukata in the $300-400 range on Japanese websites, more if they are designer works which are tailoured for the person. Think about it: the price of fabric (in America, cotton fabric often goes for $6-15 a yard), plus thread and other materials that get used or worn out ($5 or so), plus a minimum wage to make it... and all of these are again, keeping in mind American price standards in a country (Japan) where things cost much more than they do here, $150 on average for her kimono is a very good deal.
On a personal note, I can't wait to buy obishin from her! I have so, so much fabric in desperate need of being something other than a dust-gathering heap. I've been having a difficult time finding something with *quite* the right stiffness/flexibility ratio. At $1.50/metre, I can make a new obi for under $30! And before anyone asks, no, I wasn't paid to write this. Actually Tanaka-san doesn't know who I am at all. But her shop's been in my bookmarks for weeks now, and I'm so happy that I can get what I need to finish my projects without having to guess about shipping and whatnot like on Rakuten... so maybe you'll enjoy her shop, too!