Custom iPod dock mold material?

I am trying to make a custom iPod dock in my vehicle(Subaru outback 2010). There is a small change holder located behind the shifter knob, this is where I would like to put it. I need a type of molding resin that won't adhere to plastic but at the same time holds shape well. I plan to be able to pour to resin into the change holder with a iPod cable up the middle and shape a iPod shape so it fits snug. Any ideas?