It's not too hard to make yourself a 30t granny to fit the 100 mm BCD. A few people I know have done it, by starting with an existing 74 mm BCD ring and adding 5 new holes.
Here's a little Flickr album showing how I made mine.
I also made one at 29t once, but that's a bit impractical, stick to 30t minimum.
I also drill Campy cranks to take 86 mm BCD Stronglight 99 granny rings. Only goes down to 28t but that's as low as I want on a Record triple anyway. For the older bikes I have put them on, I like that it uses only parts that were available in the early '70s, could plausibly have been done then ("period correct"), tho I'm not a slave to PC-ness.
For the granny "stand-off" bolts, yes the real Campy #818 bolts are expensive when you can find them but there are lots of alternatives, such as Stornglight 'Mygal' bolts which are either still made or at least still in the retail pipeline. You might need to go to a Euro or UK seller to find them. Normal industrial shoulder bolts such as from McMaster-Carr can also be made to work with a little modification, ask for more detail if interested.
If you want your crank drilled at 74 mm, Bob Freeman of North Bend WA has a drilling jig that makes that mod pretty easy and very precise. I don't know what he charges but it's probably reasonable. He knows all about which McMaster shoulder bolts and spacers to buy, and how to make them work, so he's your one-stop shopping for Campy Triplizing.
And let's not forget BF's own Jon Vara who makes the
Red Clover triplizer for 144, way simpler than drilling your crank and searching for stand-off bolts/spacers. And it's a fully-reversible mod, the crank is not harmed!