I stumbled upon this website which has a lot of information and sources for Ancient Greek and Imperial Rome. Of particular interest to us and how I found the site is a list of some lead glandes finds with inscriptions written on them. There are some great ones like "A gift for the Asculans" and "There's Hell for you, damn you!" Those ancients had a sense of humour for sure.

What's particularly interesting is that the website looks even older than our dear forum but it's still being updated in the year 2021

http://www.attalus.org/index.html

http://www.attalus.org/docs/cil/movable.html
(You'll need to Ctrl + F and search for sling to find them or scroll down a lot. THere's a hell of a lot in there.