3D scanning + photogrammetry

There are two ways to get a real world item digitised so that you can use it in a 3D package or game engine without creating it from scratch: 3D scanning or photogrammetry.

3d scanning involves a way for the camera to measure depth, often using an infrared sensor, while simultaneously recording video. Possibly the cheapest 3D scanner can be made from a Microsoft Kinect camera, plus an adapter cable. Second hand Kinects start from about £12/$20 dollars from places such as CEX or CashConverters.

Photogrammetry can be done with a smart phone or DSLR and requires the software to create the model based only on multiple still photos or video, without the infrared depth sensor.

It is quite likely that you will need to tidy up the object once digitised, sometimes going so far as to re-topo (re-topology) which involves overlaying the scanned object with a new mesh you create in quads at the resolution/poly count optimised for your game engine. Maya has good re-topo tools.