I have been searching for the same type of mount but cannot find one. In fact I can't find any mounts for large TVs that do both a pull out and pull down motion (would also like it to pivot/swivel but I don't need tilt). The other makes and models previously suggested do not pull down (or at least I couldn't find one that did). If anyone knows of such a mount please post a link or the make/model.
BTW, the TV I have is the Samsung HP-T5064. And for the curious, the reason for needing this type of mount motion is for the TV to be mounted above a cabinet (kind of like a buffet) that must stay in place, then pull the TV out over the cabinet and drop down to a better viewing height for watching movies.