J&L has one shown now in their "New and Noteworthy" livestock listing - it's a mimic of the Eibli dwarf angelfish. There are other types of dwarf angels that Mimic Tangs mimic, and they all look different. They also take on various colour forms when they mature, if I remember.
There's some info on them at wetwebmedia as well.
http://www.wetwebmedia.com/acanthurTngs.htm
Here's the one from the J&L site:
