What to buy:
So what to buy in a city as small as Blokzijl? You'd think there is nothing really, but there is. Make sure to get your hands on some Blokzijler Brok. It famous around the whole area and if I'm not mistaken only for sale in Blokzijl, hence the name ;-)
Blokzijler Brok tastes a bit like the dutch speculaas, a (and I quote the dic here...) sort of spiced cookie. Very brief, but it tastes much better than it sounds. If you've tasted speculaas, and you like it, you will love Blokzijler Brok.
What to pay: € 2.39 in the supermarket, which is very decent since you get quite a lot!
What to buy: There are quite some shops that sell typical Dutch 'prullaria' or odds and ends in the little streets that are so many in Blokzijl.