Small Truck Camper

Look at the side profile of your cargo area, the slope pretty much precludes fitting a camper unless custom built. It also does not have adequate payload capacity.

I would go directly to mfgs site-
armed with your rigs capacities and box size, see what fits.
https://travellitecampers.com/

Also Capri-https://capricamper.com/
They make small light campers. Mounted thru floor I think.
I also was of the opinion the ridge wasnt really meant to carry any load. SUV with an open rear?
Contacting companies, they should be more than able to spec what you need as far as vehicle

a Ridgeline is not really a "pick-up truck" because i believe it has a continious body line from fron to back... but more over I have never heard of a tie-down system for a Honda R-line. There needs to be a separation between cab and bed for the Happi-Jac setup or an underslung frame type a la Tork-Lift.