Adding a GPU To a laptop

Hey Ive got a Alienware M17 and was wondering if its possible to get another GPU in there, Ive got two 3870's, and i wanted to add a 3870x2 mobility in there.. i know its possible but i don't know where to get them.. Even then i might as well bring in the dual 3870's. Only reason i want to stay away from this, is that with experience with dual x2 gpu's. Last year i built a cheap system with an AMD 9850 Black Edition Quad Core with dual 4870x2's. I had multiple overheating problems with them till i took off the stock cooling and put a thermal-take liquid cooler. Anyways because liquid cooling isn't very feesable in a laptop, short of bringing along liquid nitrogen... Anyways let me know if you know anything...