Pkgs wrapper for adding env vars

Help
1

Suppose I install the package pkgs.foo in Nix (with home-manager), which provides the binary ${pkgs.foo}/bin/foo.
How can I add a wrapper (in a nix-way) so that when I run foo, it executes: VAR=bar foo ?

2 
home.packages = [
  # Do not add pkgs.foo directly; the below is a replacement
  (pkgs.runCommand
    "foo"
    { nativeBuildInputs = [ pkgs.makeWrapper ]; }
    "makeWrapper ${pkgs.foo}/bin/foo $out/bin/foo --set VAR bar"
  )
];

All the things you can do with makeWrapper.