A barely used Hyctopson (really!) Wireless Dog Doorbell.
See here: https://www.amazon.com/HYCTOPSON-Training-Wireless-Waterproof-Communication/dp/B09CYZKKL1/ref=sr_1_5?crid=1L285S3H874YA&keywords=hyctopson+wireless+dog+doorbell&qid=1655471937&sprefix=hyct%2Caps%2C143&sr=8-5
Our AussieDoodle pup didn't make the connection to the button and the door. To be honest, it was probably because we also have a hanging metal bell right next to it that she uses to make one of her humans open the door. Whether she wants to go outside or not...
The kit includes everything you need - two buttons and the chime and button mounting hardware. The buttons can be taped to the wall or other flat surface, and the chime plugs into a wall socket. And a 'clicker' for training.