but be careful you have some way of making sure 
they line up correctly.  I always line up the 
left edge of the cel with the bottom edge of my 
scanner, so I know I have a nice straight uniform 
scan every time.  Then piece the scans together 
in Photoshop or some other photo editing software.

As for cel bags, you will most likely have to 
measure your cel length and width, then search 
online for "arcival bags" and find the size you 
need.  If you have an art supply store near you, 
you may want to call them also.