[Six]

Zacco platypus?
http://www.fishbase.org/summary/speciessummary.php?id=7762
always for sale at the size you're referring to, but can get larger.

or it could be any number of giant danio species- there are many.

GL!

 

[Six]

http://www.practicalfishkeeping.co.uk/pfk/pages/show_article.php?article_id=447

wow, they do look similar. I take it you've seen them available? Pretty cool looking.