Battery Replacement - Precision 5520

Hello to everyone.

I have a Precision 5520 workstation, the truth is that the laptop is simply fantastic and I am very happy with it.
As is to be expected in a daily work workstation, the battery is reaching its useful life also the Dell power management  recommends that I replace the battery,

On the DELL website I can't find the right battery, has it happened to someone else?
I am looking to have the same 6 cell battery that I requested when buying my laptop.

Thanks in advance.

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