Lapress is a level 56 rare silithid that can be found wandering above Hive' Regal in south eastern Silithus. (I have indicated where he can be found in red on the map below.) He drops the typical green item and decent experience for levelers. He shares the same model and color scheme as many other silithid mobs in the game. He is tamable by beast mastery hunters, but there really is no need to search specifically for him. The Hive'Regal Hive Lords who patrol around nearby share the exact same model. His spawn time is also supposedly fairly long.
Lapress is also one of the three rare spawns that can be found in or around the Hives in Silithus.
Hive' Ashil - Rex Ashil
Hive' Zora - Zora
Hive' Regal - Lapress
Lapress can be found with NPCScan. You will need to add it, his NPCScan ID is 14473.
When you do come across him, he'll be easy to spot as he is quite large compared to the other npcs around him.