I picked up a NIP Hudy bag for $35 last Feb.
....there was no way I was going to pay full price for one, but for that kind of deal, I really couldn't pass it up. It's a good bag, but it really is roomy. My Ofna blue top starter box, fuel bottle, ignitor, pit tools, temp gauge, etc...all fit in, and I still have room for my 4PK as well.
One of my good racing buddies has the Mugen bag, and while it is a bit smaller (the Ofna box will only fit if turned on its side), it's still a good bag. If I had to choose Hudy or Mugen, paying full price, I'd get the Mugen bag. I really do think it's the better bang for the buck between those two.
Now, with that being said, there are a good number of useful tool bags at Lowes, Home Depot, etc... They may not be RC specific, but they will indeed work just fine for what we need them to do. If functionality is more important to you than "image", look there first. If nothing suits your fancy, then go for the Hudy or Mugen, whichever one you can find the best deal on.