As yakky said, a polish will restore some shine. What you are looking for is a wax or sealant to keep it that way (as stated above). I agree that if you like to shop online, as MDRX8 said, Blackfire wet diamond is an excellent choice. I have recently been using Autoglym Super Resin Gloss Protectant, which is working out very well and very comparable to Blacfire Wet Diamond. As far as waxes go, OTC, I personally like Mothers Reflections, which is easy to apply and remove. If you like to shop online, My personal preferences are Pinnacle Souveran, Dodo Juice (little expensive) and Chemical Guys Butter Wet Wax.
It is important, however, to keep in mind that sealants will typically last longer than a wax, and applying both will not hurt anything (as far as protection). If applying a wax over a sealant, it sometimes "mutes" the shine a tad.