What is a 'power supply noise filter'?
Surge Suppressors are commonly available as consumer units.
Power Supply Noise Filters are not particularly common as a consumer unit, though they are commonly available as parts to be built into commercial electronics.
You could simply use a better-built 9V DC supply which has a filter built in - it's fairly common to have one large-amperage 9V DC supply powering your whole pedalboard (if you have a few pedals), rather than individual wall-warts for each pedal. Those will normally have excellent filters.
For test purposes (it's expensive beyond that) you can also use a 9V battery to completely eliminate the possibility that power supply noise is a problem.
As to the question of &quot;what a power supply noise filter is&quot; it's usually 3 capacitors and 2 inductors in a package. You'll find better results searching for &quot;EMI filter&quot; usually. But I seriously doubt you need to go buy one, if you can even find a &quot;plug and play&quot; packaged for consumers version.