I should perhaps warn you since I'm in the same 
race that finding G1 cels is HARD.  They're 
extremely rare, and when they do pop up, they are 
EXPENSIVE.  Your best chance is to try Yahoo 
Japan Auctions or Ebay.  That's where I've found 
them.

The reason for their rarity is two things:

1.)  The main reason for their absence is that 
most of the series' cels were destroyed in a fire 
at the building in which they were held.  Those 
that weren't burned were water damaged.

2.)  This is second one I've heard, and it could 
be a rumor, but I read somewhere that alot of the 
remaining cels were scrubbed down and reused for 
other series.

In other words, not only are the cels you and I 
want going to be hard to find...those who want 
them are NOT going to be selling them anytime 
soon.  But for the time being....good luck!

-Chaotic Serenity