Why Apple didn't design this in as an option I'll never understand.
As I explained in my last post, using a Mac Mini as an HTPC hasn't been quite ideal until now. The Magic Trackpad plus the Wireless Keyboard make ideal bedfellows for the mini in the living room... If only they were joined at the hip.....
Achieving this isn't too difficult. The most desirable factor for this is that the two should be as rigidly attached as possible, yet the bond can't be permanent, since you wind up with the power button of the keyboard jammed right against the battery door of the trackpad (or vice versa if you're left-handed). So some sort of Velcro attachment is the best mechanism I could think of. The only trouble is that velcro can shift laterally to some extent. So I went with a 3M product called Dual-Lock. It's like velcro, except that it's genderless and since both sides of it are made of stiff plastic, it tends to be much better at holding still.
I found the stuff at Orchard Supply (Home Depot didn't carry it), in a two-pack of 3"x1" pieces (it's actually a 4-pack - there are four pieces, which makes two complete fasteners). I also bought an 8x10 sheet of .Lexan. I used a hacksaw to make a 6"x3" sheet and attached one strip to each end and two about a half inch apart straddling the middle. I then stuck the mating pieces on, peeled back the adhesive and stuck the keyboard and trackpad on.
So, There! I fixed it!
It's not absolute perfection. With the whole thing in your lap, you notice that there's really nowhere to rest your palms, like there would be on a real laptop. And you have to watch out that your left pinky doesn't accidentally contact the trackpad and skitter your mouse pointer off on a tangent. Also, because of the thickness of the whole thing and its proximity to the bottom of the trackpad, the rubber feet won't ever touch the desk if you set it down. This makes the mechanical buttons in the trackpad useless, unfortunately. But if you don't provide a stiff support for the bottom half of the connection, it won't be as stable as this solution allows.