DNA testing is becoming more popular in the Netherlands. Many Dutch people test at MyHeritage, though some also test with other companies such as Ancestry, FamilyTreeDNA, or 23andMe.
To find Dutch cousins, you can take a DNA test. You will then get a list of people who tested at the same company who share DNA with you. The more DNA you share, the closer the relationship. See the article Dutch DNA testing strategy for more information to maximize your chance of finding cousins.