Eh...sorry if the title of this post is a little hard to read--it's because I really want others to be able to find this info when they do an Internet search 'cause I sure couldn't find any info about anything like this!
I wanted a way to hang/hook/hold/stick/mount/something! my portable hard drive onto the back of my MacBook Pro's lid/top/case/display/whatever. I wanted something that I could attach and remove quickly and easily and that, when removed, wouldn't leave any traces of its presence on the laptop (so no modifications of any type to the laptop). I was more open to modifying the portable hard drive case, but I wasn't wild about that. Really, that left me only 2 options: suction and hanging hooks--and what I discovered is that the best approach is a combination of both: suction for the portable hard drive and a hook to hang it all from the laptop lid. :) I found a wreath hook at Jo-Ann that is perfect! Check it out: