The gold standard in prepping is to have a bunker. There are many manufacturers that have sprung up that will make customized in ground bunkers, if you have the money. There are many factors to think about when purchasing a bunker, such as land, money, hiring someone to build what you want, hiring someone to put it in the ground, etc. By doing these things, there will be people who know the location of your bunker.
There is a mobile solution that is amazing! This system is called a Concrete Canvas Shelter. The shelter is made from canvas that is impregnated with concrete. Once delivered, this shelter can be deployed by you, to any location, and set up by 2 people. The Video below shows you everything about this system. I have found several dealers for these shelters which are listed below.