How much money do you have to spend on material? Ideally something like D2 would be better. Hardox is OK. If your going with hardox you want as hard a grade as possible, a hardox 450 disc with a sharp edge hitting another slab of hardox 450 with a flat edge wont do your teeth much good!

Look on google for local tool steel supplier's and see if they will sponsor you an offcut big enough. I'm sure someone would help you out . Once it's water cut then get another loacal firm to harden it slightly (surface ideally).