The uboot and loader files are within the image. You can extract them (boot folder), they should also have been copied to your flash.
KB16248 may help. It's SRX650-specific, though, so I would not expect these addresses to be the same on a SRX210H. Someone with a working SRX210H may be able to pull the addresses for you using
nvram getenv boot.upgrade.uboot
nvram getenv boot.upgrade.loader