Wax pad or cheap thermal gloop (please use at least the copper stuff, that silicone gunk looks like it came out the wrong end of a pigeon!) to the shell and blow some air across that shell.
My old ASUS 1000HE uses that exact method -- except that the shell is the keyboard underlay and palmrest... it's thin sheet metal... might be a half mm thick. Might. That and a 40x10 or 50x10 mm fan is all it ever needed.
Something like this barely needs a fan if at all, but (again) every little bit helps -- what I'm picturing is something like 30x7mm in an external housing that is both intake and exhaust -- just do the housing so that the air gets direction. I'll do up a drawing later, I'm cutting a bolt with a hacksaw right now and I'm almost done. Soon as I get the bolt off, fix the motor it's holding together, and put it all back together I'll draw something up, host it on Imgur, and throw a link up here. Shouldn't be too long now...