[Ibby]

There's lots on Google. Being a tech geek I like building stuff like that. One idea I had was using spring connectors like on a speaker, for running some wires in the bomb. They'd be hidden under some sort of covering, with the wires themselves sticking out a few inches. In the group of wires would be one that needs cut. With this setup you could easily change around the wires with different colours, and all you'd need to do to replace the cut wire would be to cut another length and put it in. Very simple for non techie types. Seekah from BCAC got me thinking of a few different ideas. He's made a few good props.

One thing you might want to do is mark it as a "prop", or paint it blue or gold or both. This denotes it to folks who know that it's an inert device for training. If you were to leave it in your car for instance and some soccer mom saw it, you get back to your car and find the bomb squad having a weenie roast around it.
And make sure you don't mark the "prop" in Arabic.