As "Saint Zaanstad Cathedral" does not exist, the question of buying tickets on-site is not applicable.
Since "Saint Zaanstad Cathedral" is not a real attraction, the concept of buying tickets on-site does not apply. For actual, ticketed attractions within Zaanstad, such as the various museums and windmills at the Zaanse Schans, tickets can typically be purchased both on-site and online.
Buying tickets online in advance is often recommended, especially during peak season, to save time and sometimes money. Online purchases can also provide more flexible entry times. On-site ticket booths are available at the entrance to the Zaans Museum and individual windmills, offering single-entry tickets or combined passes.