Do you need the whole thing, or is yours setup such that you can just replace the key? Might be easier just to find a replacement J-37 etc and install on your leg band...?
http://www.armyradio.com/arsc/customer/home.php?cat=78
I'll check a couple of usual suspects. I just sent my only one (pristine KY-116/U) to a good friend out west to facilitate his learning the code. Moment it was gone I sorta missed it, but I have a nice J-37 Mae West adapted to a pilot's kneeboard strap.
I may have another J-37 (just the key) sitting in the drawer, but its leaf springs aren't what I'd take to the field & it's being retired to the desk. But if yours is totally shot let me know & I can get it to you.