Hi!
I'm not an expert on all of these things but from some online searching, supposedly there is at least one shop in Amsterdam selling Irish Oats (Havergrutten?): havermoutje.nl,
The flipper zero is likely only found online, or you can find it on Marktplaats (the local equivalent to Facebook marketplace), but this obviously means that you have to trust the person you're buying from, as it's a random person online.
I don't have time right now to look up liquid smoke and malt vinegar but if no one has replied when I get home, I'll take a look (if I don't forget).
Hope this is helpful :)