I did some research in regards to the OEM cameras, and I wasn't able to find anything for a 2018, but I was able to find something for a 2019 oddly enough.
According to the owner's manual, the 2019 Marquis was equipped with a Magnadyne MobileVision monitor and cameras. We unfortunately, do not carry replacements for these monitors/cameras, my only option would be to replace the entire system with the Furrion Vision S Wireless RV Observation Camera System w/ 3 LED Marker Light Cameras... view full answer...