In doing so, I found a carton of NOS Electric Eel-type cable connectors. This listing is for the female (concave) connector. (Male and slot-tip connectors listed here on eBay under their own listings.)

Some may have a little surface rust from being stored several years in a closed box on a high shelf. But, hey, you're going to send them down storm and sanitary sewer lines anyhow...

Spring-loaded snap connectors are all installed, and all have the roll pin partially inserted.