the 'dream_bum_spi.tar.bz2' have a uboot binary but no sure if any one tested so I would not depend on it.
FWIW, I am running this version of u-boot. I wrote it from a working u-boot, so this doesn't really help with a bricked device. Just FYI that the newer u-boot version in that file seems to work fine. I haven't really looked to see what changed.