Here's an idea that came from a participant on the NYC the UPshot photo safari. If you need some protection for your lens try using a beer cozy! They are inexpensive (see link below) and are made of neoprene so they offer your camera just enough protection. For those who like to bang their camera bag around it's perfect!
Unfortunately they don't really come in different sizes and they do not close on both ends; this is a plus for some because it makes it faster to remove your lens.