Not really possible. For Alexa to work, it needs to constantly listen and have an internet connection.
If you’re disabled in some way and you depend on smart home appliances, it might be worth looking into having a raspberry pi control the lights, or looking into a locally hosted smart home ecosystem.
Unfortunately, it’s not possible to have the echo ecosystem ever be even remotely privacy respecting as even if it didn’t listen to you it would need to check and store your light switch status on the cloud, and it would always be possible for someone somewhere else to connect to their servers and control your lighting. Sorry 