Awesome build!
1) I'm 90% sure the D ring holder is fabricated. Like from metal or wood or plastic. And they found rivets that are long enough to go through the block and into the graflex tabs.
2) The clamp body is rubber hose. Honestly, I think any black material will work, and I would prefer plastic or metal as rubber hose can break down over time. The clamp itself looks like a fabricated block with a bent plate holding the card on top. The plate was probably screwed/glued to the block underneath the board.
3) no idea on the emitter piece, I hope the RPF can figure it out! (it can be made from aluminum C stock)