While many of these cheapo switchers will produce a bunch of noise, if you're powering only logic circuitry, the blessing of 'noise immunity' from the logic family will allow you to ignore most or all of this noise.
One answer is to find a common mode choke, put that in series with both the +5V and GND terminals, and then put a shunt cap system after that. This will significantly reduce power supply noise, and add little ESR that could reduce your 'end of the day' supply voltage.
Barring that, most modern switchers only produce a couple dozen mV of noise, which is within the typical noise immunity range of logic. Proper shielding, grounding and bypassing will make that irrelevant.
Another idea is that a lot of logic these days runs on 3.3V, so with a 5V input, you can use a modern LDO regulator next to your logic to make a "nice" 3.3V rail, and hopefully ignore most of the noise from the raw supply. This is probably the highest performance, lowest cost and "smallest parts volume" answer, given the cost and bulk of passives like CM chokes and filter caps.