Need help getting an ID on this mad lad

[LaPReptiles]

Found this amazing little dude earlier, ive got a stomatella and this isnt him for sure. He isnt a lettuce as far as i know. Who may he be? Hes a very pleasant guest to have, hes caused no trouble and is quite the looker. Friendly and clean, i rate him a 10/10. Where can i get another?
Bunch of pics on that post

 

[fishguy242]

hi welcome to the reef going to love it here!!
lots of fun/info/fun/help/fun..
looks like sea hare/sea bunny ,very cool.. :)

 

[samnaz]

Elysia cristata or Oxynoe, perhaps?