Firmwares for the REB1100 can be found here
under the links 'ram 305 original' and 'ram 305 rus' (modifed 3.05 with russian fonts). I think ver. 3.05 is the last firmware produced.
These websites have a lot of information on the REB1100 and firmware and such:
Firmwares for the EBW1150 are encrypted and property of ETI. As such they are not of any use, info wise. The ETI website has a copy of the latest firmwares for the EBW1150 and REB1200.
However, the russian site ebook.org does have a post about russia'fying
the fonts in the REB1200 firmware by Goldy dated March 9, 2008. I have a copy that firmware, but it is of no use to me as I don't speak/understand russian! I love my REB1200 just the way it is, thank-you!
The attached image shows the english translation of Goldy's post.
There was a program to dump the ROM/firmware on REB1200's that were on version 3.3 or earlier called "reb12dump.zip"; however, it no longer works on recent (v4.x) firmware versions.
As an aside, does anyone have a copy of the (unencrypted) 4meg REB1200 ROM from v3.3?