They are dropped by a NM in Palborough Mines named Qu'Vho Deathhurler. I just got these about five seconds ago after seeing the NM and thinking 'I've never seen/heard of this thing...' Took him down as 22nin/bst. He put up a bit of a fight but wasn't too horribly hard. No idea as to the place holder and all of that since he was just standing there when I came into the room. I think I just might be the first person to own a pair of Guerilla Gloves! :D
EDIT: After running around in Palborough for my Quadav Backscale I came back into the room I had first found him in. He was there again (Map #2 H-6). I fought him again and didn't get a single drop. I did however get 60 exp and 24 gil. Good luck to anyone deciding they also want a pair of these! He seems to respawn in about an hour or so.