Amsterdam is famous for its red light district, where women sit in the windows and offer their body for money. The city is not that liberated that gay boys have rented their own window to attract customers. They have congregated in various clubs around town. Brothels are legal in Holland, which means they get the regular inspection for e.g. fire safety and hygiene.
We list the following clubs with boys (unfortunately, we can give you no advice about their quality nor their prices):