Hi Rahulz,
I just bought a bag from ebags (
eBags - Largest Selection Of Handbags, Backpacks, Luggage & More - eBags ) which is a great low cost place to buy camera bags. They're always running sales and they have great video demonstrations of the product.
The one I bought for myself (through ebags) was the Tenba Messenger, which allows top access to the camera via zipper, without the need to open the bag wide so that everyone can clearly see that you have expensive camera gear inside. If you're wanting to be discreet that's a good way to go.
Lots of good camera bags, backpacks, etc. are demonstrated by video at the Tenba web site (
Tenba: Professional Bags for Photography, Computers, Shipping, Portfolios and Grip ) if you're interested, and they're pretty much all available on ebags, or Amazon, or whatever your preferred store is.
Everyone has their own preference as to a camera bag. My own is to have it slung over my shoulder to one side (not in a backpack) so I can see where it is at all times for safety reasons. I also don't want the bag to *look* like a camera bag, so that it doesn't become an easy target for thieves.
I also won't buy a bag online that I can't see demonstrated in a video. Buying/trying in person is best, of course, so that you can feel the weight of the bag, get a true idea of its size and figure out if it would be comfortable to carry. And of course it's always a good idea to patronize local camera shops, since the Internet is taking such a big bite out of their sales.
For the K-x and standard lenses any bag that can comfortably fit a DSLR camera body and an extra lens or two should work. Many bags allow you to store the camera and telephoto lens as a single piece (for easy retrieval and fast picture taking) and that has always been my preference.