I must admit the other day I tried my D700 with grip and my 300 f2.8vr and it did fit in the Nikon CL-L1 bag, the only thing is there is not enough further adjustment to have a TC fitted also. I have used this setup since, and the padding of the Nikon bag is superb. Failing that I use a Lowepro Vertex 200aw, but this may be a bit big for your requirements.May be worth getting something big enough to hold the lens with camera attached. I bought a Lowepro rucksack that holds my 500mm but did not consider leaving the camera attached. Luckily it does fit (it is a tight squeeze though)
I keep the lens / camera in the rucksack all the time. Just pickup the bag when I am heading out.
I bought the AW500 but they do smaller (so cheaper) versions.
Dave.
Check Amazon - Lowepro do bags for lenses up to at least 600mm - so I am sure your 300 will be catered forCheers for the replies guys. I was hopefully looking for a case just for the lens with no body attached but looking at the Lowepro bags on WEX there doesn't seem to be one large enough.
Daz