The matter used in the printer comes from the ship's own stores. Strictly speaking, nanotech is a reality, but it's not a very useful reality just yet. No independent nanite colonies able to follow complicated programs or host AIs; data storage media and processing power haven't yet shrunk enough to be viable. Instead, a fist-sized colony of dumb nanites (which are so dumb that they're illegal to use for mass production inside a gravity well, out of fear for a gray goo “Sorcerer's Apprentice” scenario) chew through a dense block of metals to generate the raw materials for everything from ship fuel to spare parts in an act of nanoalchemy that would make Paracelsus green with envy. Shipboard printers handle turning those raw materials into finished product, and any waste matter gets dumped back into the alchemy tanks.
The only essentials that don't originate from the ship's matter block are Sitri's food, supplements, and medicine. It's bad enough that she has to subsist on flavored protein cakes and nutrient powders (mixed in water to the consistency of a thin milkshake), but the idea of eating tasteless nanoformulated bricks the texture of sand is enough to make her want to heave. Almost half of her remaining personal cargo mass after the printer has gone to a large box full of candy bars, gum, and other little indulgences.
Meanwhile, the Joyeuse drifts complacently through the void, hopping from rock to rock in the asteroid belt. Approximately once every Earth revolution, a set of low-power laser arrays spark to life and saturate local space with a burst of ultraviolet light. Days, sometimes weeks of absolutely nothing are punctuated by a harried half a megasecond or so whenever some of the laser light bounces back, pinging an asteroid's profile.
Today, for the first time since Sitri got out to the asteroid belt, two signatures ping back. Two asteroids, moving on notably divergent paths, are almost within visual distance of one another. Most often, multiple pings mean a close-knit asteroid family, which are far too risky to exploit.
Most people still think of the asteroid belt as something out of old science fiction movies and video games: a dense mass of rocks the size of small office buildings, spinning sedately in Solar orbit and constantly at risk of being struck by anyone who dares to venture within its bounds.