Quoted from RebelGuitars:

I used this power distribution system from Pinball Life;
https://www.pinballlife.com/accessory-power-supply-for-stern-spike-spike-2-system-machines-backbox-mounting.html

Quoted from craif:

The power supply is the same as commercial machines, but it doesn't have a filter/capacitor board and there's reports of lights dimming when a lot of coils fire together such that unless you really enjoy it, it's probably worth considering whether you want to just run it off a DC adapter plugged into the wall initially. Probably won't matter in most cases, but especially for a topper where you'll be dealing with wires outside the machine anyway no reason to be a guinea pig. If you enjoy testing such stuff as much as playing pinball, there's some discussion a page or two back about adding an oem spike2 or aftermarket filter setup earlier in the thread, but with it being so new I don't know of anyone who has actually tried it yet.

Quoted from craif:

Somewhere I'm sure. But it's all originally coming from the 48v psu and getting converted down and the flicker some people are getting suggests that when the game is running and a lot of coils fire together the draw 48v draw from the flippers is pushing the surge capacity of the tiny filter caps in the built in PSU and causing a brownout (at least) in the lighting which depending on the bulb is usually 5v, 6.3v or 12v.
The power filter boards in commercial machines have huge capacitors that charge up when draw is low, then feed back into the system when draw is high to smooth out spikes in demand so that doesn't happen. Toppers just have a lot of lights in them which if the system is pushed already will push it even further.