Inspired with a suggestion about using AC/DC power supply instead of toroidal main transformer I didn't bid for one on the eBay (that was also suggested) but check what is offered from regular suppliers to insure more predictable availability. I find Mean well's LRS-150-48 with price that is pretty attractive (possibly because it does not include PFC).

If we compare it with typical toroidal transformer (that is tree times heavier then two AC/DC PS) we have the following situation:

How it looks in practice? With output load of 4 A I got the following output noise without anything else (i.e. common mode choke at the input nor ferrite bead on the output cables as show on the picture above):

Actually even without anything connected, and when output is disabled noise that somehow comes from LRS-150 is present on the output:

But when common mode choke is added at the input of the power board it starts to look much better:

... or with different time base: