Getting back to the original question, try Pierce Manifolds for "soft mount" kits. Cheaper to buy whole kit than just O-rings. They also have what looks to be a better option. However, they are a bear to install with carbs in place, and those O-rings dissintigrate and crack over time. That was my experience.
Advice from Ireland was to use paper gasket only. Original Ti and CS came with bakelite insulators and gaskets on each side - prob better but depends on clearance available. I read elsewhere that float bowl vibration in DCOEs was more of an issue with race applications (high rpms).
I bought new carbs from Ireland - maybe not the cheapest, but at least you are dealing with knowledgeable and approachable people.