I think you're in for a challenge unless you can swap out the existing lockset with a standard mortised lock or deadbolt lock.

Hager makes some electric strikes designed to work with dead bolts.  I've used them a long time ago at several commercial projects.  They're big and clunky, but work: [Link: hagerco.com]

If the client would like to have the door swing both ways, you could remove the stopper that's installed and then use a magnetic shear lock.  This could be concealed in the door and jamb instead of being surface mounted like most mag locks and the mechanical lock would be redundant.

The shear locks are finicky to get adjusted, but work well in metal doors.  If it was a wood door/frame, I'd advise against the shear mag lock because any shift in the door or frame will cause it to malfunction until it's readjusted.