I think I am the only person that doesn't overthink this.
This is what I use.
Hahaha, mee too but, I use crocodile clips and a stripped DC wire from the adapter
I've got a DC plug/adapter to fit at some point but I've been using it to power all sorts so the crocodile clips works great for now.
I do like the PC power supply idea as well though, I've got access to loads of them as well.