I dont like the idea of setting the DC of items too high to find.
Well, unless the chance of finding a thing is 100%, you
are "setting the DC too high to find," you're just randomizing
when it's too high to find.
And that's fine, if that's what you prefer, but it's fundamentally no different than just setting a DC.
You see, if you decide there's a 70% chance a searcher will find an item, you're saying there's a 30% chance they can't. Also, unless you're adjusting the chance based on the searcher's skill, you're taking control of the player characters away from the players. (That is, I can't make a character who is better at searching than other characters if
all characters have the same chance of finding things.) If you
do adjust the chance based on the searcher's skill, you're doing exactly the same thing as when you set a DC.
If you set the DC to find an item at 25, for example, you're really saying "only X% of searchers will find this item." Or at least, "only X% of searchers who spend Y amount of time searching will find this item." The only difference is that players who have chosen to make their characters be good at searching will more often fall within the X% than those who haven't. (And there's no difference at all if you're adjusting the chance of finding the item based on the searcher's skill.)
As I've already pointed out, the only real difference is that when you set a % chance instead of a DC,
not even the DM knows until the roll is made if the searcher will find the item.
If that makes the game more enjoyable for you as a DM, go for it! More power to you. Just be aware that depending upon how you go about it, you may be taking away your players' ability to play a particular type of character (the highly observant detective/trapfinder/whatever), and that if you're not, it probably doesn't make any difference at all to your players that you're not setting DCs.