I uploaded my result, i'm not totally happy but well it was a try
The markets your referring at, are held on queensday *koninginnedag* in almost each and every town in the Netherlands, here in my city it's most kids that sell their toys, they are called free markets. They start selling as early as 5 or 6 o clock.
It's a GREAT way to buy awesome bargains, I usually go out at 6 in the morning to score the best things. We always make a 'seeklist' like special books from certain writers, or that 1 special toy the kids miss, and usually we end up with a car full of things for only 25 dollar or something. mostly books, toys for in the yard, and last year we also had 2 great gazelle bikes for the kids.