I'd be inclined to use fiber optic or Tritium boosted fiber optic sights over something needing a battery... with the yard lit, regular fiber optics should work, but he could try it at dark with the yards lights, & see if they light up enough ( even if he had any other gun with fiber optic sights, it would give him an idea, before buying something specific )
I'm assuming the rifle is top eject, the sights I recommended will work well with this design, otherwise if you are talking illuminated scope, you'd likely need side mounts, etc.
I have several Williams Fire Sights on several different guns, I'm partial to the ghost ring style, but a traditional rear fiber optic may work better in darker than hunting light ???
In life you either make dust or eat dust...