I never would have thought of photocopying the 
cel!  That makes it easier than sending someone 
the cel to get it done exactly.  I wanted to add 
that if you do have someone do it, you should 
decide whether you want the lines done on the 
side facing the cel (could stick with certain 
types of inks) or the far side of the cel (lines 
more likely to scrape off).  For the lines to be 
on the side faacing the cel you'd have to have 
the image flipped though, but that shouldn't be 
too hard at any photocopy place; my work 
photocopier does mirror imaging.

If you can't find anyone else to do it, I might 
consider helping out... I just really hate 
cutting down the cardboard to package full sized 
cels *mutter mutter* Photo mailers are soooo much 
easier...