xapt is already in Squeeze as part of the pdebuild-cross package:
$ sudo apt-get install pdebuild-cross
$ man xapt
$ /usr/share/pdebuild-cross/xapt --help
The change is to enhance xapt and put it into /usr/bin but the enhanced
version will still only support installation, not just downloading.
xapt is faster, cleaner and much simpler than apt-cross. It does this
by dropping most of the complexity of apt-cross and therefore some of
the functionality.
Is there are reason you want only to download and convert manually?
Note that xapt does not support excluding certain packages from
conversion - this is the main source of bugs in apt-cross and the main
reason for it's removal. xapt downloads and converts all dependencies,
even those which dpkg-cross would not normally convert. It doesn't
actually matter, as it turns out, at least until we can replace the
whole package-renaming-cross-hack with a sane method.