I did some more surfing, but couldn't find the tool. However, I did see a variation of the two pin method that works on the double fold binding. Silly me... when I first saw the pic, I thought you were to run the fabric through the hem ruler; which could work I suppose. :0)
http://creativelittledaisy.typepad.c...ersion-of.html
Here's another video with guide marks.
http://www.fromwootoyou.com/2012/12/diy-bias-tape.html
Although it is for bias tape you can adjust the measurement and folding for double binding.
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Found it!!! Sorta..... here is how you can make your own tool.
http://stitch-n-smile.com/how-to-thu...as-tape-maker/
Much cheaper than the plastic templates. Whew! Now I can stop searching.