Best place to get a grinder : r/AmsterdamEnts Reddit
The above is true, but I'm joking. You can go whereever you want and get one. Some coffeeshops will give you one for free for a 50e+ purchase. Go to CS "The Stud" (Molukkenstraat 581), they sell Futurola Grinders for 1€. They also sell really good weed, so get some bud from them.