You might try here:
Braumarkt | Everything you need to make wine, beer, liqueur and dairy
They do kit, nut you have to search for them. Postage is on a decreasing scale. The more you buy, the cheaper it is. Certainly not worth buying just a tub of steriliser, but stock up on your kits, extract, hops, crown corks etc and they're quite competitive.
Also the Netherlands doesn't really have the same pub culture, or at least not to the same extent, so pub closures are not causing a run on homebrew suppliers.