That puts me on the right track - thanks. The NGFF or whatever "regular" M.2s are called are 5 / 28. The NVMe M.2s are 5 / 29. Thank goodness for cell phones where I can take a picture and zoom in about 500%. I think the 5/28 connector is referred to as the "B" style, and the 5/29 connector is referred to as the "M" style. There some "B+M" slots on the PCI Card adapters, so there's hope.
I'm not done searching yet, though. Unfortunately, that adapter I linked to above goes to a U.2 connector, I'm looking for one that will connect to SATA. Most of the adapters I find have this quote at the end: "Supports SATA-bus NGFF M.2 SSD with 'B' key or 'B+M' key, Note: This item can not fit with PCIe NVMe/PCIe AHCI M.2 internal SSD with 'M' key)." I'll keep looking...