I know it’s the old round pin we used for phones back in the day but can someone send me a link to the exact one because I’m seeing too many round pin charges of different sizes. Also where do I go for tech help related questions like these? Is this the right community?
If you know the lamp model number or manufacturer or anything like that you could possibly find the specs online somewhere. I think they also sell some "universal" type barrel plug power supplies that come with various sized barrel connectors.
Ah yes, you must mean the biblically accurate universal barrel plug adapter.
Edit: I had something like this guy growing up and used to use it to make sparks and other shenanigans.
What utter goofball was it who ever built a device with reversed polarity?
Some Chinese devices come with reverse polarity.