Flush Mount Volume Knob to Vinyl Siding
I'm in the process of installing some outdoor speakers for the deck. Additionally, I'm going to install an outdoor volume knob for the speakers.
What I would like to do is mount the knob similar to the way my outdoor receptacle is mounted (See Enclosed Photo).
I'm looking for the white box that's surrounding the receptacle. My plan is to use a similar box and put the knob in the middle of it.
My question is, what is the white box in the picture and where can I get one? Is this some component of vinyl siding? I've looked in the big box stores but no luck.
Thanks for any clues.