Here's the one I've got, American DJ PC-100a:
http://tinyurl.com/xnlv
It may be cheap but it works fine - $39.95!

Thanks to everyone for the responses. After I figured out what they
were called I was able to find them on Musician's Friend.The one I
ended up buying was indeed the American DJ PC-100a -- mainly used for
lighting rigs I guess. The box makes it look like a piece of crap toy,
but I imagine there's not much to this device. I have it plugged into
my Furman AR-1215 voltage regulator/power conditioner and my problems
are solved.

And to answer the guy who wanted to know WHY I wanted to do this:

There are many reasons. The main being that there are often long
sessions in the studio where I am mixing and don't want to leave my
tube preamps burning up into the night. I guess I just like being in
control.

Thanks again everyone.