Anyhow, being a cheap bastard and considering the cheapness of the keyboard itself, I decided to try to fix them myself rather than getting replacement keys. My solution might not be the best one, but slight modifications will make it worthwhile.
What I did was cut small strips from a PCB board to make a new support for the broken key joint
As you can see, the PCB layout makes it extremely simply to cut to size.
Finally, I used Super Glue to fix them together.
The keys work well now and feel very ‘safe’, but somewhat stiffer. A thinner piece of slightly softer plastic might ‘feel’ better, although I prefer hard to mushy. I also have this idea in my head (might be wrong though), that the little holes in the PCB strips get filled with glue as well, providing further support for the key. Dunno..