Well, now I have three Pass Scarves and TMs for Struggle Bug, Pluck, and Thunder Wave, but have yet to have gotten either of the two hold items I want.
Then again, I'm not entirely certain you can even get them in the demo, but considering I've only gotten one of numerous other types of items after over 12 hours of the demo, they could just be extremely rare...
EDIT: Also obtained a Bulldoze and X-scissor TM, but no new hold items. I have noticed, however, that I've started to get four star difficulty dungeons a lot more frequently, and they do seem to be more prone to giving out good rewards.
If someone does actually manage to get X-ray Specs, a Pierce Band, or Gold Specs (Or whatever the item that lets you see gold bars on the map is called) noting which dungeon it was a reward from would be extremely helpful, as certain items seem to be found only from certain dungeons.