Cleaning kit or repair kit for guns

I have been wondering if there is a possibility to add some type of gun cleaning/repair kit to replenish the life of the guns we purchase/find in city. I know there are quite a few people myself included that like to collect guns and would like to be able to somehow restore them so they don't waste away. Also with the guns from the holidays/events around the city would be cool to collect but they currently have a durability and after x amount of time they expire and are rendered useless.