Tour to (or via) Afsluitdijk

A good way for those that really want to see the dike is to take the bus and get off at the monument stop to catch the next service an hour later (till 8 PM now, check when you plan your journey.) Alternatively, travel to either end and walk onto the dike. You could rent a bicycle to ride onto the dike for a short distance, (see below)¹. The bike lane is just above road level on the side of the higher dike and a bit protected from the worst winds but is known to be windy anyhow.

¹I do not find bike rental places close to those busstops, but you could google for the bike shops and ask if they have a second hand bike you can rent for the day.
Many bike shops do some rentals even when they do not advertise the fact.

Public domain photo of the Monument and the dike, attribution on this page

There are several tours advertized that include the afsluitdijk, but as the English language users are not happy with that word they do not all include the name in title or description, often they use a translation but I have seen different ones, one of which is 'Enclosure dike'.

The better search word to look for might well be 'Friesland' or 'Frisia', the province at one end of the dike, the one Amsterdam is not in.
Most tours that include both Friesland and Amsterdam and go a full circle will use the long dike one direction and go south of the water (old land or polders) the other way.

Maybe a little bit late, but there is a tourist bus 'Afsluitdijk Tour' I just got a tourist book on Amsterdam and it includes a tour from Amsterdam to the Afsluitdijk, Medemblik, a steam train ride to Hoorn, a city walk in Hoorn and a busride to Amsterdam. Leaves at 9.30 from , costs €55 and takes 8.5 hours. Runs from 21st May to 28th of September the office is on the Damrak