Thin silk cloth from a nice used dress packs VERY small and light. You can have a rag of about 18"x18" and it packs down into the crevices of your tool kit.

It's very strong and can be used as a tire boot even if doubled-over.

I also add a couple of individually-wrapped alcohol wipes for after-maintenance road clean-up. They also work fairly well to clean a wound.

The thing about 8-speed chains is spot-on. They cost 1/2 as much or less, and last 2x as long. I can't imagine anyone touring across the country on a 9+ speed drivetrain. You'd have to stop at least once to replace chain and cassette.