Mutoh XP-501 pen-holder stub

I bought a cheap-o Mutoh XP-501 pen plotter and it came without the pen holder. Doah! Anyway, I made this, which fits in the pen-holder slot and fakes out the sensors, so the plotter will start up and be happy. Once the plotter has started up, you can send a file to the plotter, but you need to open the lid just before it starts drawing and manually insert a pen into the pen holder mechanism.