Unfortunately, the answer to that question is:
"...from another H3**"

The best bet is to try and find a non-functional device for sale for parts. At least then you'll get other parts to scavenge as well as time goes on, but I understand that these are hard to find, and reasonably expensive. This is not the ideal solution, but as far as I am aware, no other solution exists. Perhaps another forum member has a device, or parts thereof, they would be willing to sell you.
Fingers crossed.
[Saint]