Daffodil Markers

The recent onslaught of rain and rising temperatures has resulted in a plethora of Daffodils sprouting in the garden. We don't have any flowers yet but there are some promising buds. The only thing is there are still some crowded clumps. And after checking the internet, I'm supposed to divide the bulbs in the fall - long after I've forgotten where they're burred. So what kind of plant markers do you use? They need to stand up to squirrels, kids and summer weather, as well as blend nicely into the landscape. Any suggestions?