If your looking for a soft sided single pistol case that will hold one pistol and 4 mags, Cheaper Than Dirt has this one. http://www.cheaperthandirt.com/CASE050-1.html
The price is right and it fits your description. I bought the double cases for 2 pistols and six mags. I sometimes take 3 or 4 guns to the range with me, two in each of the double cases and then I put them in a larger range bag with the rest of my gear. It protects all 4 in the larger range bag. If your just taking one gun and 4 mags with you, then this will work great, but what about your ammo.