Thanks for posting these... widgetsupply in particular seems to be a great source for hard-to-find stuff, and great prices.
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Yes my dad was a source. He used a similar screw bit to secure locks during the construction project. Are they really so hard to come by?

http://www.hobbytool.com/Products/Weekly%20Specials/3033.htm
http://www.widgetsupply.com/screwdrivers/hex-bit/hex-bits.html

Matt