Scroll binders are made by players. Most shards should have someone selling them. They look like red PS/deeds.
I believe the number goes up as the scrolls get bigger. Something like 8 or 10 105s to make a 110, 10 or 12 110s to make a 115. It's been a while and I don't have one handy to check.
You can also use them to combine Scrolls of Transcendence, though those just add up (and you can't use them until they hit 2.0 or a higher x.0 number).