Just saw this item on Amazon, which is a case with a built-in keyboard:
http://www.amazon.com/Bluetooth-Keyb...oard+bluetooth
Funny, though, since it looks like an original Fire in the picture, which wouldn't work with the keyboard. (Edited to say: looking at the image again, it might be a pasted on HD screen over some generic tablet. The Bezel on the bottom doesn't look long enough for the HD, and there's no sign of the camera).
The amazonbasics one looks nice, but of only 2 reviewers who used it with the HD, one couldn't get it to work:
http://www.amazon.com/AmazonBasics-B...oard+bluetooth