If you want to really do it up, use a flyback transformer in a DC/DC
topology.  The flyback is one of the few solutions that will generate a fixed
output form values above and below the target at the input.  In addition, they
are inherently energy limitted in the case of a short circuit at the output.
Try surfing around at premier magnetics, at www.premiermag.com, and see what
might fit your wishes.  You might (cross fingers) get away without a custom
wind.

Chris Eddy