I have the same problem.
The kernel you're looking for is just the Linux kernel that comes with LTIB, linux-2.6.35.3, built with a special initial ram disk and some IMX bootlet code to load it in recovery mode. If you're still using a distro old enough to run LTIB on your development system, then it's easy to build the updater.sb and updater_ivt.sb files, as described in section 2.5 of the "i.MX28 Linux BSP User’s Guide" that comes with LTIB.