I went to HD today to return something I alread purchased a while ago
They have 3 kinds of fan switches with timers. $19 to $29.
Two kinds are located where they have a big display of light switches and the third was back where they have the bathroom fans.
For $29 you get a 7-button switch6 buttons with times ranging from 5 or 10 minutes up to one hour. The 7th button is a toggle for on/off. The cheaper ones have fewer buttons. These are the rectangular type and would require a plate with a rectangular cutout. You can get one with two rectangular cutouts(one for this gizmo the other for a light) or one rectangular and a small toggle for the light. Of course you could put the light on the timer so it didn't stay on until the next time you show a guest where the bathroom is. Always check the bathroom after your guests leave. I had someone once who didn't flush, prettty rank after a week
, now I check.