Here is what I've made so far (actually, the last state the project was in since I had no more time for it):
https://www.dropbox.com/s/9o8192ad5vdma ... ToLvds.zip
Schematics and PCB are made in DipTrace (it's free). It uses an 18 bit LVDS interface. You can switch to a 24 bit lvds by changing the LVDS transmitter. Some caps need to be added on the supply rails (they are not in the schematic, as many other things, I've added them later).
Note: The HDMI connector pins are backwards. I've fixed this making my own male->male hdmi converter which I used directly with the Pi. So the PCB will need some updates to work ok with a regular hdmi cable.
The converter needs 3.3V to work.
If anyone makes an order of PCBs, I would also be interested in one piece (maybe free for the work I've done