Fan timer with "stay on" option

[lark@xxxxxxxxxxxxxxxxxxx (Lacustral)]

Is there a fan timer that has an option to just leave it on?  I'm planning
to get a bathroom fan, but I also want to be able to just leave it on, to
use it to clear air out of the house generally.  The fan wouldn't be more
than about 2 amps.

I'm sure it's also possible to set up a circuit to bypass a timer that
doesn't have a "stay on" switch.  How would one do that?

I want a quiet fan timer.  Someone told me of a timer which goes up to
12 hours, but they said it makes noise.  So something electronic, maybe.
Something quiet that goes up to 12 hours would be fine, as long as it
also lets you leave the fan on for only a few minutes.

Such a thing wouldn't have to be a *fan* timer specifically, any timer
that has a "stay on" option that is good up to 2 amps or so would work.

Thanks
Laura