I'm a little confused on this one. Are you running DCS on 2 rail, or DCC? I am used to seeing DCC on 2 rail, but I suppose it would be theoretically possible to run DCS.
If what you mean is 2 rail DCC, then you need a DC power source. You could make an AC to DC converter to use transformers you already own, for not much $$$, but if you are looking for a plug and play solution... Have to see what the 2 rail guys say. I don't have any idea what the recommended brands are.