Josh chase at the Mercedes swap shop had replacement flip key is on sale through the end of July at 30% off. I got a flip key for a little under $200 after shipping cost. If they are truly unavailable then I got mine at just the right time. We should still be able to get transponder valet keys that will start our cars… SOS was charging $65 for them when I checked over the winter. As for the lock and unlock circuit boards, from my research it seems that DK 55 bored cannot be reprogrammed by the user or a locksmith. If you can obtain a virgin board it can be programmed by someone who has the proper equipment and software. I bought a 2007 sprinter K55 three button flip key fob which is identical to the crossfire OK thinking I could program at to lock and unlock the doors and use it as a keychain with a transponder valet key. The programming instructions in the owners manual seem to only work to pair a remote that was already programmed to the vehicle. I have not checked with the Mercedes dealership to see if they could erase or virgin eyes a used remote and reprogram it. It may be possible but the cost probably would have been as much as buying a replacement flip key from the Mercedes swap shop or SOS.