Yes officially there is no other way other than proper support contract ID or SAID with HPE you can't download firmware from HPE website.
I don't know what is your current firmware running in the P2000 array otherwise you may need multiple versions as well to make the system up to date with firmware.
If you know what exactly firmware version you need then you can Google it to find the same if anyone shared or uploaded to any public wensite but there is some risk factor always there as people may include Trozan or similar type of virus along with those firmware files. The moment you download them in your system your system gets impacted by this virus so always better to download firmware from HPE website by buying proper support contract with HPE. For example, I found the below links but not idea if they proper link or not (Totally up to you if you wana take chance or not as I haven't verified them),
http://get-file.info/q1a/?q=p2000g3+firmware+download
https://fliplitlesite.web.fc2.com/hp-p2000-g3-firmware.html
https://megabestarchi.web.fc2.com/hp-p2000-g3-firmware.html
Hope this helps!
Regards
Subhajit
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