HP 82241A charger replacement polarity

[edwincool2]

Hi everyone, sorry to jump in on this thread.
I recently acquired an 82240A printer (having so much fun with a DM42), and I was looking for the AC adapter.

Does anyone have any experience with non-original chargers?
I found one on amazon made by Kircuit, you can find the link here: https://www.amazon.com/Kircuit-Adapter-I...B081SP325G

Is it worth it? Will I fry my new printer?
Also, in the manual it specifies not to use the AC adapter without batteries. What is the reason for this?
Thank you.

Greetings,
Edwin.