In many cases it's not the electrical noise but the fan noise itself which makes it harder to hear. most fans I've used hooked up to my 12VDC power supply didn't introduce any noise.
I recently discovered this stand on Amazon - Allsop Metal Art Jr - I put it in another post on the forum as I thought I had struck gold but apparently multiple members had already known about it
I can mount the radio on the top or below (it has holes so you can stick your mounting screws through the holes. Also they provide venting. Then I mounted fans (I guess you could either mount them above or below depending on where you mount the radio).
Nice thing about it is that I can mount a mobile radio + amp to it + fans + I can fit my switching power supply underneath and it keeps everything nice and organized.
I preferred buying larger 12V fans as then I can get more airflow as many of the small laptop platform ones are too small and loud and also fail (from experience trying to cool my laptop)