After some thought, your only options are
1) Backpack - hot and sweaty, not particularly large and affects your posture. I've ridden with a tramping (hiking) pack to move my toolkit about, and its not ideal. A smaller day pack would work better, or even a hydration pack if your load is smallish. Some people like sling-style messenger bags.
2) A fanny pack / bum bag / waist bag / hip bag. Not very large in capacity.
3) Frame bag - These fill in your main triangle and fasten on with Velcro/hook-and-loop. The loops shouldn't damage your carbon because there is no bolt clamping force. Downsides they block your bottle cages, and in side winds they can be sails.
4) trailer - as mentioned in another answer.
5) Freight - At each place you're staying, ship yourself a largish courier bag with clothes and whatever, with the expectation of picking it up on arrival. You can shove your dirty clothes in and ship it back home. This has a fairly high cost, but means you travel light. Plus you have to plan ahead for what you'll need. Not a complete replacement for the others, but may allow you to get away with the fanny pack alone.
6) Go ultra-light - take as little as possible. Wash your stuff in the motel overnight. Wear your oldest most ratty clothes, and chuck them out after a couple days, after you buy new clothes (note: order is important here)
7) Thanks OJS for this one - a saddle bag which hangs most of its weight on the saddle rails, and only an anti-wobble strap around the seat post. Downside, they may interfere with the back of your thighs while pedalling.
Any other suggestions?