Hi guys,
I'm not sure if such a thing exists, but really want to get a relay circuit
that keeps power to a device on for some preset amount of time (say, 1 hour)
after input power has shut off.

Why do I want such a thing?  I want to wire it up into the 12v supply for
the fridge, so that I can have the fridge running on 12v, and make short
stops for gas/lunch/whatever without the fridge losing power, but also
without me running the battery down because I forget to shut it off.

A Google search will turn up a lot for "time-delay relays", but, as far as I
can tell, none of them are quite what I'm talking about.  (There are some
that wait some time before coming on, or that only stay on for a fixed
amount of time once power starts.)

I guess I could probably wire something up from components, but I was hoping
there might a "plug and play" solution.

Thanks!
-Wes