These devices are listed in the Table of Hardware:
pepe2k's modded u-boot works on this device. Download a precompiled binary here (unpack before using). Follow the upgrade instructions in pepe2k's README. This version of the bootloader has a functional httpd application that allows you to upload new firmware directly to the bootloader from your browser (similar functionality to other routers that have a function-by-number menu in the bootloader for flashing firmware).