If you have a series connection, then it is normal for all the lights to turn after turning on the switch. If you have a parallel connection, then that's the time that you could add another switch intended for the other light.
Here is a link from the Amazon. https://www.amazon.com/s?k=bidet+for+toilet&crid=I29EUQE74ZD2&sprefix=bidet%2Caps%2C609&ref=nb_sb_ss_i_4_5. I hope you can find one that suits your needs. It costs less than $100.
Oh that's a lot of stuff there zannej. I wish that the painting activity will start soon so that you guys could move forward. By the way, I'm happy to hear that the person living in your friend's house tested negative for COVID-19. Stay safe always. :)