I am pretty sure I bought mine on eBay from a dealership, years ago. I just looked back through my history, and it doesn’t show up unfortunately.
The Honda OEM stock number for that is:
75765-S30-305
I would suggest copying and pasting that number into a search in eBay or other sale sites and wait for one to become available. I did a quick search, but it appears as though all the dealerships online no longer carry it. ☹
Hopefully someone on here may have one hanging around, or one will pop up randomly soon. It definitely completes the look of the rear on our cars!