dpkg-repack is just the one, as Johnx said. I had it running on my N800 on OS2007, it wasn't too difficult. It's a Perl script. So, I had to install Perl (which wasn't there in that first OS2007 install I had), and I believe I had to do a few adjustments -- it ends up calling some other applications, and IIRC some of them are busybox versions (i.e. may not have the options used). But in the end it worked fine.

I don't have it installed anymore, it went away when I flashed the device with an upgrade. But it wasn't difficult, so if the OP wants to have a try then just grab this file: http://ftp.debian.org/debian/pool/ma...ck_1.31.tar.gz
Unpack it with 'tar xzvf', and the script is dpkg-repack/dpkg-repack
Try to execute it, and fix all the problems as you go along. Usage: dpkg-repack name-of-package