I just checked with a couple of dealers in Chicagoland area and they weren't even aware the adapters were available until I gave them the item numbers. Unfortunately, none of them have any in stock.
If you want to use parking mode you may want to consider getting a dash cam battery pack.
https://www.blackboxmycar.com/collections/battery-packs
I've used ones from Cellink and Blackvue giving me hours of parking mode capability and never had an issue with the camera's affecting my vehicle's 12V.