Where can I get more skybox textures for HL2?

[Phalanx]

I need more skybox textures specifically night skyboxes since HL2 only has 2 night skyboxes (sky_day01_09 & Sky_borealis01) and a bright and sunny day skybox since HL2 only has overcast skies. So does anyone know a good place where I can download skyboxes that work with HL2?

[Peter Brev]

Gamebanana would be a good place to start.