That's what I thought you meant, just wanted to clarify for others that may read this thread in the future and start searching for a non-existent attachment.
Here are some pictures of the inside of the clutch unit for the O&R Tarpen Mini Engine power-head, the rear housing & clutch drum are the OEM parts for this...
... and the rest of the clutch & engine mounting are standard O&R parts.
This threaded adaptor fits in the end on the clutch unit, if you have one of these and it's not seized, add some fresh grease to it to prevent this.
David