Ron, meanwhile i found a shell based ipkg here https://dev.openwrt.org/browser/trunk/openwrt/package/base-files/default/bin/ipkg?rev=1494 .
I copied it to the /bin directory, where the busybox tools are located (all the symlinks). I did a chown root ipkg.
It seems to run, but it asks for a /etc/ipkg.conf.