"apt-get source" for packages.ros.org?

edit

Where are the sources (*.orig.tar.gz, *.diff.gz, and *.dsc files) for the debs on packages.ros.org?

Specifically, how to make "apt-get source" do the right thing for packages from this repository? Adding the obvious deb-src line to ros-latest.list doesn't seem to help (see below). Poking around on the packages.ros.org http interface, it looks to me like the sources have not been uploaded.

Packages I care about include ROS dependencies like assimp, yaml-cpp, and eigen. For example,

$ apt-cache policy libassimp2
libassimp2:
  Installed: 2.0.0.6-ubuntu1~lucid1
  Candidate: 2.0.0.6-ubuntu1~lucid1
  Version table:
 *** 2.0.0.6-ubuntu1~lucid1 0
      500 http://packages.ros.org/ros/ubuntu/ lucid/main Packages
      100 /var/lib/dpkg/status
$ cat /etc/apt/sources.list.d/ros-latest.list 
deb http://packages.ros.org/ros/ubuntu lucid main
$ apt-get source libassimp2
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Picking 'assimp' as source package instead of 'libassimp2'
E: Unable to find a source package for assimp
$ sudo vi /etc/apt/sources.list.d/ros-latest.list
$ cat /etc/apt/sources.list.d/ros-latest.list
deb http://packages.ros.org/ros/ubuntu lucid main
deb-src http://packages.ros.org/ros/ubuntu lucid main
$ sudo apt-get update
...
Ign http://packages.ros.org lucid/main Packages
Ign http://packages.ros.org lucid/main Sources
Hit http://packages.ros.org lucid/main Packages
Get:1 http://packages.ros.org lucid/main Sources [20B]
Fetched 20B in 1s (14B/s)
Reading package lists... Done
$ apt-get source libassimp2
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Picking 'assimp' as source package instead of 'libassimp2'
E: Unable to find a source package for assimp