Wilwood offers an electronic parking brake that essentially replicates the electronic parking brakes we have on new cars today. The dash mounted control switch either sets or releases the brake. Not very period correct but extremely effective as a parking brake.
This is what the brake looks like;
It complements existing brakes on the axle, it does not replace them. The e-brake system has side specific calipers one each for the right and left sides of the axle.
This is the entire package including calipers;
Summit will set you back about $350 per side for everything.
Not period correct but unlike our mechanical alternatives this one works.