How to download/install pre-compiled Subversion binaries for Debian
You can extract the binaries from the deb package for your architecture (which you can download from here) using dpkg-deb -x.
So for example you can do this if you're on i386:
wget ftp://ftp.debian.org/debian/pool/main/s/subversion/subversion_1.5.4dfsg1-1_i386.debdpkg -x subversion_1.5.4dfsg1-1_i386.deb subversion
Of course you might have to do some tweaking to make it work. Extracting a package is not the same thing as installing it.