Attempting to install zwave on/off switch to run three way switch. Found out the auxiliary box has no neutral wiring running to it, anyway to get it to work? There is a separate three way switch right next to this switch but is ran off separate breaker.

Unless you can bring a neutral to the box you won't be able to utilize the specialty switch.

I think you may be able to reidentify a traveller to the new switch location as a neutral, and have Z wave control at both locations, as it is wireless and no need for travellers/switchlegs?
I took a quick look and am sure they have receiver modules, just didn't see them.