You forgot to append the most important part to that statement, and instead chose to leave it implied: "at the wage I am willing to pay." Pay your employees more money and better labor will come. So say the laws of supply and demand.
"Difficult to find" is about scarcity, but it's also about the actual act of finding. Traits like 'diligent' and 'trustworthy' are hard to identify before hiring someone. You can't test for them in the short term, and everyone wants to signal that they have them. That's especially true in low-skilled sectors like retail, where you're unlikely to have common contacts or be able to see diligence in someone's work history.
From what I've seen, those traits are hard to find in a very literal sense - even given a candidate you don't know what you're getting. This is coordination failure; raising wages doesn't resolve information asymmetries.