Apparently, my bathroom fluorescent tubes are of an unusual wattage (16 W), because no store in Zurich had them in stock and they all seemed quite perplexed that anyone had ever invented such a light bulb.
Half on a joke, half seriously, I typed in
gluehbirne.ch and found a functioning website that amazingly enough sells light bulbs. Since I was desperate to not shower in the dark, I ordered. The price was ok (I thought the shipping seemed a bit high), but I have to say, the turnaround time was fast (I ordered 8pm on Tuesday and got them this Thursday afternoon) and man, those bulbs were packed well. They could have gone through a rugby game and not have been broken. It totally explains the higher shipping charge.
They have a bunch of different names and sites, but it's all the same actual site. gluehbirne.ch / gluehbirne.com / ampoules.ch / lampadine.ch / bulbs.ch These are all the same.
So, if you are desperately in need of some bulbs and don't know where to go for those odder requests, check out this site.