I don't know how to navigate the ubuntu/debian pool system automatically, but a manual search picked out: http://ddebs.ubuntu.com/dists/precise-updates/main/binary-amd64/Packages pointing to http://ddebs.ubuntu.com/pool/main/l/linux-lts-quantal/linux-image-3.5.0-23-generic-dbgsym_3.5.0-23.35~precise1_amd64.ddeb - FChE