The Futaba low-profile servo model number is S9551. I don't think this has been out too long so you may still be able to purchase its predecessor, the S9550, as well (although I
guess the specification isn't as good for this one).
KO have got some new low profile services coming soon (the 2511 & 2512;
click here), but don't appear to have released any specifications yet so I'm not sure how these compare to the 2413.
HTH.