Thanks all for the replies. If the parts car is super cheap, I may attempt this upgrade and document it. If not, it sounds like it would be worth my time to seek out my next used leaf that is an SL or above trim that has this.
Also, thanks for including the detailed terminology. It's a bit...
I have a 2015 Leaf S with the Charge package (CHAdeMO, 6.6kW charger) and backup camera. Otherwise no options, so it has the basic Air Conditioning/Heat Pump setup for a 2015.
I see a 2014 Leaf __ (unsure model designation) being parted out locally that looks like it has the 3-way valve...