Extending a wireless signal through a Shipping Container

Hello,

I run an outdoor ice rink and our POS runs off of a private wifi in the area. Unfortunately, our admission booth is a repurposed shipping container, and we can barely get a signal to penetrate the steel walls of the unit.

I'm essentially looking for a way to hard wire a tablet (ethernet jack already built into the dock) into a router that can connect to the existing wireless network. I assume there is some sort of outdoor rated equipment that I can mount to the outside of the unit that will receive the signal better.

Unfortunately, the IT guy for the organization that controls the networks in the area doesn't seem to care much if the hardware issue isn't his hardware. So sadly, the internet is my next affordable hope. Any basic suggestions on how to solve this would be awesome.

Thanks