I've actually often wonder the same thing. Has water cooling ever been tried on a laptop? When you consider that mobile CPUs & GPUs are getting closer to their desktop siblings as far as performance goes this becomes an interesting topic. Does anyone have any idea about this?
Laptop water-cooling systems aren't feasible because they'd significantly reduce mobility... which is obviously the purpose of buying a laptop instead of a desktop. For the same reason, they aren't marketable, so you won't be able to find anything like that in retail. I think the only real solution is to buy a laptop that is designed for gaming.
Not all laptops are considered due to portability. I have an Asus G72 and it is pretty much a "perma-plug" machine. I bought it due to space saving, not portability (I don't have room for a desk & desktop in my apartment, especially with a 1 year old roaming about). I think that more people are turning to the "Gaming" laptop format more for this reason. Aternative & more effective cooling options should be pursued for this market. True it would lack portability, but it would still qualify as a space saving design.
Not that I would recommend trying this, but I do remember seeing a custome CPU cooler (for a custom desktop) that used a "copperpot" filled with dry ice to cool the CPU. Maybe it's possible to modify this concept into a laptop cooler format. I don't know how to explain exactly going about this, but if the laptop sat ontop of a "copperpot" type cooler that was filled with dry ice, one might expect it to cool the laptop better than the basic fan designs we have now. I know it sounds insane, but who knows, maybe it would work.
I've tried to use exhaust fans, by putting the ventilation output .. and reverse the direction to suck hot air exhaust is in the laptop .. and its results 50% cooler. I bought an electric-powered exhaust fan, so do not use USB power or other distinguished