I have only seen them on endurance racing cars/trucks. You might want to search for rear end coolers because they are the same thing and you won't come up with so many auto trans hitts.
I have seen rear end coolers use a small dry-sump pump driven off of the pinion yoke by a belt. You may be able to do the same on the trans if it isn't a slip yoke.
Stock car products sells the pinion yokes with the pulley on them.
No one said it would be cheep