Here:
"most British style guides discourage use of the serial comma unless the items in the series would be confusing without it."
http://grammar.about.com/od/rs/g/serialcommaterm.htm
http://www.grammarly.com/handbook/pu.../oxford-comma/
http://grammar.wikia.com/wiki/Oxford_comma
What you are suggesting is something completely different. I'll forward his to my teacher but the thing is sleeping bag is a specific type of bag. Replacing it with just a bag won't be a plausible solution because then it can be any bag.
When should we use oxford comma,
http://www.grammarly.com/blog/2015/w...much-about-it/
This explains when it will be necessary to absolutely use oxford comma.
See this is why we are fretting over style guide. It can be quite confusing.