Props generally fall into two categories; "Hero" (those that can stand close scrutiny, often with working parts and lights) and "Stunt"
Stunt Version
A “stunt” version of a prop is typically a low-quality version of a “hero” or detailed prop so that the “hero” version is neither destroyed nor causes harm to the people involved with the stunt.A “stunt” version of a prop is typically a low-quality version of a “hero” or detailed prop so that the “hero” version is neither destroyed nor causes harm to the people involved with the stunt. For instance, in the fight scene between Kara Thrace and a Number Six in “Kobol’s Last Gleaming, Part II,” a stunt version of the Arrow of Apollo (made of rubber) was used in that scene. There were two versions of metal and two of rubber made. Stunt versions of props are typically of rubber. Stunt versions of costumes will be the same quality, though specifically marked “stunt”. They may be old versions of the costume, used by the main actor and then given for use by the stunt actor, or they may be new versions, specifically tailored for a stunt actor.
http://www.propworx.com/auctions/auction-terminology/
If you simply mean a prop that has been cobbled together from parts, you may be looking for a word like "fudged" or "throwaway"