Make your own
I have found that it works best to make your own, take heavy gauge wires from the battery to the dash. route a wire to the battery negative terminal as well. Just make sure you put a fuse as close to the positive terminal as you can.
2000 C230 Kompressor
1988 190e 2.3 - 225K miles, owned for 7 years. I cannot say enough good things about this car. Very well built, even at 225 it ran like new.