Comment 1 for bug 872178

i fear for now you have to replace the hardcoded value in the jasper_setup script with a better hardcoded value ... easiest should be to just append an overlay file (named jasper_setup) with the same path to your initrd.

http://wiki.debian.org/DebianInstaller/NetbootFirmware#Squeeze_Example_.231_:_add_single_firmware_deb shows how you can easily merge 2 cpio archives where one has an overlay.