The ones I have are the WTB Dirt Drops, but they stopped making them. There is a set on ebay (although they are 25.4 dia clamp, not the standard 26.0 road clamp size)

http://cgi.ebay.com/WTB-Wilderness-T...QQcmdZViewItem

Also, webcyclery has both midge bars and mungo bars:

http://webcyclery.com/home.php?cat=455