Hello! Here are the two basic variants of the outfits worn by Citizens in Half Life 2. These are only for adults, since there are no teens/children at all left in the Half Life 2 universe, although if requested I will create them. They are based off Sims default meshes and require no expansion packs to use.
The sims pictured can be found here but I'm not sure why anybody would use 'em.
Enjoy!