They are in the game, but they are level 12 treasure. Now you may think, what the heck, there is no level 12. While that is correct, that there is no physical level 12, there are level 12 encounters. On each level, it is possible to generate an encounter 2 levels above the level you are on. This is still true for level 10. So you need to get a level 12 encounter to get those items, and level 12 encounters are more rare. Note, however that the Mithryl shield is also a level 12 treasure, so you are getting those types of encounters.