Cels Forum

Try Freddy's Cels (url listed on the second page 
of the cel guide I maintain).  I don't know his prices, but he 
has some nice cels of Guymelefs for sale (one is of 
escaflowne).  Also check Buy Now Kiki (url listed 
on the main page of the cel guide).  His prices can 
vary quite a bit, so you might find something every 
once in a while.  (one note is that shipping from Buy 
Now Kiki is 4000Y (approx. $30 US) for up to 5 cels, 
so it's best if you order a few cels at once to cut 
down on the shipping cost)  I don't remember if he had 
any guymelefs, but check anyways.  

Also try the Cels by series listing under [A-E] for 
Escaflowne.  I have listed how many cels each 
dealer has for the series.  That might help you a 
little, if you haven't tried it yet.

Good luck!

Chad Kawakami
Internet Guide to Anime Cels
http://www-scf.usc.edu/~ckawakam/cels/