Are you talking about the bit that goes in the hole next to the roll pin and is clamped by the two grub screws?
This is just a rod that pokes downwards, with the bottom tapped to hold the stylus. The stylus is a hardened triangular piece that bears on the pattern.
It has just struck me that a Vxxx carbide insert, suitably reground, might make a good stylus.
Are you talking about the bit that might replace the square green plate held on with button head screws?
This is the retraction lever. On the top, it is a lever with a knob. It clamps to a vertical shaft. Looks like it has about 60 degrees of travel.
I highly recommend buying a manual as it contains useful advice on using the attachment. It also has diagrams of both pieces described above. My own attachment is buried in the shed somewhere hence the vague reply.
If you give me specific part numbers from the manual, I will measure and draw the pieces for you. Please send me a PM with your email if interested.