Hello Quintijn,
Most of HPEs firmware and software is moving to the Entitlement process where you will be required to have a HPE Passport to access downloads. In a case like yours, the 3rd party company who is handling your support contract is the one who will be able to supply you with the firmware downloads you require.
Just as an FYI you can refer to the following page for the latest information about current firmware for the MSA arrays: https://h41111.www4.hpe.com/storage/msafirmware.html
Hopefully this will help you to know the latest firmware to request from your 3rd party supplier.
Cheers,
Shawn