moredread: i have just had another idea.
 
```
{ pkgs ? import <nixpkgs> {} }:

with builtins;

let 
  sources = map (x: x.src) archive;
  archive = with pkgs; [ 
    /* your packages here */
  ];

in pkgs.runCommand "source-archive" { } ''
  tee $out << EOF
  ${concatStringsSep "\n" sources}
  EOF
''
```