They are N/A from Honda so the only option is CMSNL or David Silver Spares or used on E-bay...or someone here.
If the piece is marred a little, no problem , it's the o-ring doing the sealing anyway. Re-use the plug & caps but install new o-rings. Use a 6 sided socket on the caps and a small vise grip on the tang of the plug.
The machined end of the oil passage can be slightly sharp & damage o-rings on reassembly, make sure to oil or lightly grease both when and be "ginger" when you reinstall the plug.