I used to find huge amounts of the champagne finish 105, it always set a bike off nicely. The grey early 105 you are looking for is pretty rare as you have found. It was only about for a short while. I haven't seen any for some years now, even attached to bikes.
I've seen it with RSX, once it was everywhere, no its hard to find. Tricolour 600, everywhere NOS, then nowhere... (i'm talking car boot sales and the tip, my small little world!)
This seems to be the case, there is the odd bit on eBay but nothing like the amount of stuff that even the rarer MTB groups seem to have. I will go for those front and rear mechs for now and I found 2 chainsets in the US but they want strong money for them.