I think the Norhtec MicroClient Jr., eBox-2300 (which is pretty much the same) or the decTOP all fit the bill

http://www.norhtec.com/products/mcjr/index.html
https://store.dataevolution.com/ProductDetails.asp?ProductCode=DT%2D7001&Show=TechSpecs
http://pcburn.com/review-NorhTec_Microclient_Jr-4.php
http://www.desktoplinux.com/news/NS4091104225.html

The supports VESA mounting and consumes 8 W. Mount it on the back of an LCD monitor and you are all set.


The problem is all these are companies out of Taiwan and shipping is $40-$50