Battery powered (not 12V) propane detector / alarm.

I need to replace my propane detector / alarm. The one I currently have runs on 12V. I tried to find one that has its own self contained battery, but could not find one. Does anyone know of / or if there is one that runs on its own battery power (i.e. is not connected to the camper 12 volt system)?

Thanks in advance for your help with this.