You have always been able to download HP customized installation ISOs from VMware, but the versions provided there were always outdated. And this is still the case: Right now the above mentioned link will let you download a version that was published back in March ...
So, let's go and build the Sep2012 version of the HP customized ESXi 5.0 installation ISO ourselves! Here is how to do it:
2. Create a new empty directory on your hard disk (e.g. C:\TEMP\Sep2012).
3. Download all the device driver zip files from http://vibsdepot.hp.com/hpq/sep2012/esxi-50U1-devicedrivers/ into this directory.
4. Extract all the zip files to this directory (when prompted you can safely overwrite any file).
5. Now delete all files from this directory except for the files named *offline_bundle*.zip. Also keep the file hpvsa.zip (an annoying special case: this is also a valid Offline bundle).
6. Open a PowerCLI prompt and run the ESXi-Customizer-PS script like this:
C:\TEMP\ESXi-Customizer-PS-v1.3.ps1 -hp -hprel Sep2012 -obDir 'C:\TEMP\Sep2012'
This will create the customized installation ISO in the script directory (C:\TEMP in this example). This ISO will also contain the latest patch level of ESXi 5.0 - no need to apply any updates after installing an HP server with it.