Yes I know what you mean, I can't fully open the1980-81 catalog on my ipad on this site so I was suprised when the 1981 opened for me.

If you keep any eye out on eBay these seem to come up occasionally. This is the one you want for Embryon http://www.ebay.com.au/itm/Original-BALLY-PINBALL-1981-PARTS-CATALOG-ELECTRONIC-GAMES-FIREBALL-2-MEDUSA-/251196354111?pt=LH_DefaultDomain_0&hash=item3a7c782e3f&_uhb=1#ht_500wt_922
I wouldn't buy this one though. Over priced and shippings a killer. Of course you can try downloading it or maybe someone nearby has one you can copy.
 Embryon looks very cool by the way. Not a very common game at all, can you post some pics? I'd love to see it and hear what you think of the game play.