3D printing

Access to a 3D printer, and some ability with design software (Fusion 360 is free to hobbyists and well worth learning) is extremely powerful.
Often a job will come in that needs a simple plastic part replacing which can be easily printed. This will often make an "impossible" repair possible for a few pence worth of plastic.
I have made new push-buttons for a transistor radio, a new gear for an electric pencil-sharpener, a new knob for an infrared oven, a replacement clamp for an adjustable reading lamp among many other things.
Some items that others have designed are available to download free from sites such as Thingiverse. An example is the wheels for Zanussi dishwasher shelves.