Alright, I got the starter problem fixed! Starts up like a beauty!
I'll explain what I did, maybe someone else can benefit from this and save themselves some time fiddling around or looking for a specific starter. This is what I ended up doing:
Since the electrician that had looked at my starter had actually clipped some wires in the magnetic switch, and it was quite buggered anyway, I decided to look for a replacement. A friend had a 24V starter in pieces and we mixed and matched pieces to test out operation. Interestingly, the 24V starter ran fine on 12V without load, but as soon as it was built into the car, it didn't do anything.
As 3B starters are quite rare down here (especially if you can't wait a couple of weeks for one to show up) and I did not want to spend the money in a shop, I looked around a bit for starters that would work with the "nose-job" mentioned before.
Turns out that all Toyota diesel starters built in the 80-90ies (at least for landcruisers, hilux, hiace, 4runners, etc) use very similar starters, even though they differ in engine sizes. Some of the components, as the clutch assembly (see picture) are identical in all of them.
On the other hand, they differ significantly in the nose cone (next picture, 3B left, 2LTE right) and sometimes in the power output. Power varies between 2.0, 2.5, 2.7kW and it is not evident which power is used just by knowing the engine type. All starters I found for Hilux's were only 2.0kW, even though the part specs show that the same car could have been sold with a 2.5 or 2.7kW starter.
I ended up finding a wrecked Landcruiser Prado (early 90's, 2.4L 2LTE engine) that had the starter wesintl talked about (28100-54090). I switched the nose cone, which was the only bit that was significantly different and it worked!
While scanning the EPC I found that there are quite a few starters that would work, as long as they have enough power. I'm not sure if a 2.0kW starter would have cranked the 3B, but I would have given it a try if I would not have found this one. Oh, and don't try a 24V starter on 12V, does not work...
Cheers!