Since my original (Analog Four) PSU-3 died, I have been looking into options for replacement power supply units. Based in China, it wouldn’t make much sense to order an original Elektron PSU (it’s overpriced anyway), so I went on Taobao and found the power supplies from the original manufacturers of the PSU-3 and PSU-3b, with the difference, that both plugs are 2.1mm instead of 2.5mm (bought adapters) — specs and model numbers are identical otherwise.
As for the PSU-3c, I couldn’t find that one. I can confirm that the two PSU-3c units I have for my Digitakt and Analog Heat MKII are indeed making an audible noise. (Didn’t notice before). So I wasn’t eager to look for those.
As an alternative, I bought a cheaper Delta power supply with matching specs, more or less for the fun of comparing their built quality and noise emittance.
Costs were around 13€
Links to products and specs (for reference, and seems possible to find the 2.1mm plug versions for purchase outside China as well):
PSU 3b = GPE024D-120200D
Golden Profit Electronics
https://en.gpetec.com/
PSU 3 = Sunny YSY1319-3012
Sunny Group
Delta ADP-36EHC
Delta
https://www.deltapsu.com/en