Even though I still have doubts, I thought I will try a new battery to see what happens. The original battery is this one: 7.2V 802316062x3 HP HFR 1600AA

https://fccid.io/png.php?id=2771752&page=10

There are plenty of batteries on amazon that look like they will replace it, like the one here

https://www.amazon.com/2gig-BATT2X-Console-Rechargeable-Battery/dp/B00JZZILRK

but I am concerned that they have a slightly different shape: in the original batteries the two levels of tree AA size batteries are shifted with respect to each other, while in the amazon one they are aligned. My worry is that the amazon one is slightly thicker and will not fit the battery compartment.

Did anyone successfully replace a battery in Gateway? If so, which battery did you use?

Thank you!