I'm looking for something that will hold one pistol and 3-4 mags.  I want to be able to toss it in the car, or in my backpack, and be certain that my pistol won't be scratched up.  

This is not for long-term storage.  



Specific requirements:

- Hold at least 3-4 mags

- Material: Soft cotton or nylon.  I don't like PVC material, like the Midway bags.  PVC seems like it could hold moisture.  

- Padding: ~3-4mm.  Plenty of cushioning.  

- Separate the mags from the pistol: no rubbing/scratching possible

- About $20 or so



There are so many different brands out there.  5.11, Drago, LA Police Gear...  But not many photos or reviews.  

I have several of the LA Police Gear Pistol Cases ($9.99).  Fits your criteria (not sure about padding thickness) and they are very nice for the money.
Buy one and see if it works for you.