Ship operators are wise to lay in a few tons of “spare parts” - pipes, tubes, wires, plates, mechanical assemblies, etc. These do not have to be specified, unless the players or referees want to. These will take up space in the cargo area, but some things could be argued to be held in the ship's locker.
After a ship is damaged in combat or after a breakdown (see the article “Starship Malfunctions” in JTAS #15), repairs will consume the spare parts in one-ton lots. The referee can determine how many lots of parts get used up, depending on the nature and severity of the damage.
Spare parts are usually purchased at a starport, on a world of ship's TL or better. If a ship is going to spend a lot of time in an under-developed region, it should have lots of spare parts aboard.
Standard parts lot: Cr 1000 x (TL-7). e.g. A lot of TL-10 spare parts costs 1000 x (10-7)= Cr 3000.
Spare parts can be scrounged anywhere (see the illustration above), with Streetwise skill providing a bonus to finding them. Scrounged parts can cost far less or far more than standard. PCs should be encouraged to negotiate deals for pricing; NPCs may demand the PCs do a 'job' for the parts. Qui-gonn Jinn could have negotiated with Watto for the hyperdrive and avoided the whole podracing distraction.
Of course, any time the referee wants to he can decide that a specific bit of technobabble is not available in the spare parts stores. The PCs will then have an adventure to track down the necessary part.