I've keys to padlocks for about five of my accounts; three others leave the keys hidden under objects in their gardens and two houses I climb over the gate and unbolt (no padlock).Speak to your customers and inform them of your difficulty. If they're awkward; drop them; though I'm sure they won't be; none of mine were.
I can't climb over the gates as i've got a trolley system
use a database to text. a few clicks and everyones notified