After poking around at some OEM electric parking brake solutions it looks like some are using Tesla rear calipers for parking brakes.
Calipers can be found for $50-$100/pair on ebay...
https://www.ebay.com/itm/Tesla-Model...EAAOSwnlRewe4a
A company sells a controller for them with a few actuation options...
https://www.pantera-electronics.com/epbcontroller.htm
You're on your own for brackets in most cases.
The calipers operate similar to a reverse polarity power window, and I had a spare window controller laying around so I'm going to try using that and see if it works. 2-way momentary switch, 1 way for engage and the other to disengage.
https://www.amazon.com/Directed-Elec.../dp/B00H4N1Y2O
I like the e-stopp idea but if cables can be eliminated completely that would be ideal.