Hi Pilgrim, welcome to the site. As has been mentioned on here other places, a Remington 870 Express pump action youth model would probably fit well, cost about $220-$250, and can be found at a lot of stores. Just shop around till you find the best price.
However, for a few more dollars I would recommend you shop around at gun stores and gun shows and look for a used Remington 1100. They will sell for $300-$450 depending on condition. For many years this was THE gun to shoot at skeet/trap when you were talking about autoloaders. They are very reliable, kick lightly, and if they do break almost any gunsmith can fix them up very quickly. Good luck with whatever you decide.