If so how do I do this?
I see a lot of weapons people port over and would like to add them to maps I play

You'd probably be best to create a mod, package all the stuff in the mode then use

AddZombieBoxWeapon(<weapon>,<weaponModelName>,<isDualWield>);

To add them to the box, as wall buys, I would assume it to either be impossible or INCREDIBLY tedious.