SilverPas

Anyone know where to get one?

xr4tic

They do make external trans coolers, but you'll have to plumb it in yourself.

Mat Indukts Lambos

S4's also have an additional cooler on the back side of the driver's side intercooler. If you have a 1.8T, for example, you could get an S4 left IC and the trans cooler & lines, and install that, in addition to the one in the radiator. I'd say it's serious overkill though, unless it's a track car, and then I'd say why aren't you driving a stick? :-P