google some images, once you find one you like save the image and open it up in say.... photoshop, or paint. Blow up the image to whichever dimension you want then print it out. You might have to print out a couple pages before you find the size you want.
My friend gave me a template its 19" length 71/2" at its wide point and 2" thickness. I would find some curved shapes you could use to trace on to a piece of poplar or I was thinking some cedar would look good. So mark out your center wide points and tail and nose wide points. Then take your curved edges you found and connect the dotes. He also used contact glue and old wetsuit fabric to make a grip for his hand. It seems like the longer the length the more plane you can get on the wave.
Here you go...https://www.dropbox.com/s/zu756cs9gjapu8o/Handplane%20Template.jpg. I'll post the dims in a bit as well...basically a Danny Hess template....by far my favorite template.
