How to flush the toliet without using the hand to touch it at 41 000 feet.

Flight information date.
Date: May 26 2024.
Airline: Zipair.
Flight number: ZG1.
Aircraft type: Boeing 787-8.
Registration: JA828JA.
Origin: Honolulu, Hawaii.
Destination: Tokyo (NRT), Japan.
Flight time: 7 hours and 55 minutes.
Seat number: 56D (Unfortunately, I don't have a window seat because window seat is sold out, but flight is 85% full).
Taken 1 and a half hour, before landing in Tokyo (NRT) located at the very rear end of the plane on the right. I can't remember how many lavatories on the plane, my guess is 6 to 7. If anymore knows how many lavatories on the plane, please let me know in the comment, so that I can change it, thanks.
It's my 1st time flying Zipair flight number 1, it's good.