Thanks for the ideas guys,
I struck out at Radio Shack. They hav 18V at 1A and 1 that is lower, but only 800mA.
For the variable, I don't think that will work for me. Some background:
Historically, I have run my bump and go trolleys on DC. This means relatively high speeds, to have the momentum to trigger the reverse. This Christmas I set up using an MTH infrared lockon. The performance is AWESOME! Better than using the variacle knob on AC. I think it has to do with the way the AC is chopped by the knob vs the was the IR system does it. Anyway with the IR lockon, I can be slower and steadier than with DC or the AC knob. With the Z1000 outut, the minimum voltage out is 5V. If I can lower the input, I can get a lower start voltage. So I think the variable output on the Lionel supply would defeat the benefits of the IR system.
Why you ask? Because I run a NY Giants trolley above the TV. If I can make it quieter, I can run a trolley all year!!!