Anyways, the Nvflash on the phone is the Linux i386 binary. The bootloader.bin isn't platform specific, as it's meant for the target, rather than the host. THe archive is available in /usr/local/share/motorola/fireboxmake/OSH_tools.tgz.
Unfortunately, this is where we get stuck, because we don't currently know how to get a connection to the phone. And that's where all of you come in! Can you get further? I've gotten this far:
Nvflash started rcm version 0X4 Command send failed (usb write failed)
Update: Information I've obtained indicates that this is the error you get when the SBK you pass in doesn't match the SBK on the system. So, no luck until we get that SBK.
Update 2: Additional links from dasmoover:
Credit to dasmoover for the find.