This older but working adapter is for my trusty old T460 Thinkpad laptop which sadly failed last year after many years service. It has a round 7.9 x 5.5 mm power connector, see photos. [My newer replacement Thinkpad has a different power connector]. See link for compatable model Thinkpads. Output 20W 4.5a.
https://www.amazon.co.uk/Charger-ThinkPad-IdeaPad-Notebook-Adapter/dp/B0CGR...
AC adapter for Lenovo Thinkpad Laptop (Eastney PO4)
This offer has been gifted to someone and is no longer available.