While in the short-term biodomes and encounter suits will keep somebody alive, somebody who plans to be in a given environment for a long period of time needs to adapt so that it simply isn't hostile anymore. One step towards the "void-born" is the Arctic Life Blood Adaptation, which is a genoprotein modification that converts the iron basis of a person's blood to chloroflourocarbons. It also adds a stronger silicon content to the body overall in order to preserve the flexibility of a fluid structure at superlow temperatures. This system means being able to survive as low as a hundred degrees Kelvin (though this would be freezing cold for them), but also makes live above freezing very uncomfortable. A "hot day" for someone from a cool climate would be deadly to somebody with this modification. However, if you exist on a subarctic world, this makes life reasonably functional.
Tech Levels: BioTech 5, NanoTech 3, StringTech 4. For StringTech 6, temperatures consistent with the void of deep space are survivable (though air, radiation, high speed particles, and the like are still possible). For StringTech 8, the character can move and act freely in absolute zero, though not indefinitely (it's still freezing cold to them).
Cost: Expensive, though it's usually inherited.