Being an ‘18 you have a couple of options. Have the dealer order it and pay his mark up or use trekwood and replace it yourself.
Repair is usually to replace. There should be a sticker on the inside of the door that will give you the dimensions and probably a part number.
Replacement is straight forward, remove the screws in the frame, pull old door off. Clean sealant, apply new butyl tape to door frame. Put screws back in.
2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.