It is not all that pretty, but what is called "wiremold" will do the
trick. A channel that runs on the surface. Corner and joint pieces, and
boxes for the fan, and connecting into the power. I needed outlets in a
closlet recently for my computer printers, which I wanted to hang on a
wireless print server. Out of sight, in that case. Standard item in any
good electrical supply house, or Lowes, Home Depot, etc.