Here a link to the Collegehills wiring adapter kit I used (page 3) and the horn kit (page 1) for anyone interested in a plug and play set up.
http://www.collegehillshonda.com/category/2016-2018-honda-hrv-accessories-aftermarket.html
And the Stebel air horn, they make a compact truck air hon too
but it was too big to fit in the HRV's left horn location.
https://www.amazon.com/Stebel-11690019-Nautilus-Compact-Black/dp/B00CMX20H4
http://www.collegehillshonda.com/category/2016-2018-honda-hrv-accessories-aftermarket.html
And the Stebel air horn, they make a compact truck air hon too
https://www.amazon.com/Stebel-11690019-Nautilus-Compact-Black/dp/B00CMX20H4