Okay, I've skimmed over my narration and, though you could probably make a case that there are more, I found 15 ITEMS that have an invisible

next to them.
There is one that only
Eomer can spot (if his memory is good enough to stretch back to the game he modded), and there is one that only
Enca can spot.
So that leaves 13 for the rest of you.
(actually, one has been "found" already but has not been completed- the name of the village)