Override pxe_dir for single OS


I need to pull some pxe files out of a non-standard Ubuntu directory
layout. Any idea if this is possible without subclassing the
Operatingsystem::Debian class? Ideally I'd like a parameter I could edit.
Any other ideas how I could achieve the same effect without resorting to
"underneath the hood (i.e. not visible to the foreman user)" tricks?