There are also other server PSUs, but they are rare in germany. Make sure, that you isolate the chassis from each other and don’t cause any other short.
Just an example. If you buy used, they can be even cheaper. They are highly reliable and can supply their power for long time. I’ve ordered my odrive but it hasn’t arrived yet. I’m going to use a high power lab bench psu for testing and 2 of those in series. In theorie, you could also use them in parell, but that’s not safe. They also usually have a second 12v rail.
But I’m not sure if they need an external signal to power up, but shouldn’t be a problem.
One thing is that you may need to dissable your grounding, which can be dangerous. You need to figgure that you when they arrive. You can also try isolating the case from negative supply or remove the case. It’s dangerous, but cheap can’t be safe.
Edir: looked it up and it can be kinda dangerous, so own risk and supply might blow up. You may need to do some research, but you need to do some things that compromise your safety, I just say it’s possible.