RPC1(dot)org is up for me in the U.S.
How odd that it's not available for you in your location.
Looking around the database, I do not see firmware for the OEM drive (GWA-4165B), but there is some form of firmware for the retail equivalent GSA-4165B.
On The Dangerous Bros. site (hosted by RPC1(dot)org), there is a "beta" version of RPC1 firmware for the GSA-4165B. In order to crossflash the drive and make use of that firmware, you might have to use a Windows machine to do the flashing.