eBay has the Proform 66792 Positive Stop Tool, https://www.ebay.com/itm/Proform-66792-Piston-Stop-TDC-Tool-14mm/162870453759
Autozone has it, https://www.autozone.com/test-scan-...ator-tool-for-spark-plug-hole/750719_0_0
O'Reilly's has it, https://www.oreillyauto.com/detail/.../66792/4658996?q=Proform+66792&pos=0

But it has to be ordered, which means I have to wait, which is why I am looking past this troubleshooting step. I will order one, but we won't have answers for 10 days or more...