So I got the free legendary mantis blades from the cyberpsycho area downtown as soon as the map opened up. After that, I could not find any other mantis blades in any of the ripperdocs. I've visited every single one. I've been watching some let's plays and I am seeing people with less progress in the game than me visit ripperdocs and see rare and epic mantis blades in their stock. Think I've got a bit of a bug.