Just thought I'd mention that you do get the 
original Production Sketch(es) when you purchase 
the Rilezu cels.
I've just come back from holidays in Japan. There 
is a store in Nakano that specialises in Rilezu 
and some reproduction cels.
I had a look at the Aoi Yori Aoshi Rilezu cels 
there and they all included the sketches.

Other series that they had Rilezu cels for at 
that shop were:
- Get Backers
- Samurai Deeper Kyo
- Somedays Dreamers
- King of Bandits Jing

Prices ranged from 10,000Yen up to 30,000 Yen. 
Aoi Yori Aoshi stuff started at 20,000 Yen.
I picked up a Somedays Dreamers Rilezu cel for 
10,000 Yen which was pretty much all I could 
afford with my budget.

I'm not sure how you could purchase those cels 
unless you actually have a friend in Japan that 
could pick it up for you or you make a trip there 
yourself.

I can give details about finding the shop if 
you're interested.

- X