I really like Exie, I'd use it if I used Exuperantia as a full name.
Reasonably, anything with -ex- in it...
Alexandra ->
Lexie -> Exie /
Alexandra ->
Lexa - > Exa.
You can probably get away with using them on their own too, since it's kind of obscure.
"than you will go to jail for kidnap."
top: Celeste & Grace
bottom: Pearl & Infinity
http://www.behindthename.com/pnl/59411