Touring on a Bicycle: Sleeping Bag options

On my first bicycle tour in 1994 I used a low end Walmart style sleeping bag and I was not completely satisfied with the result. Early in August I was camping in Yellowstone Park and it was below freezing and I froze my butt off in that sleeping bag. Sleeping bag technology is head and shoulders above the 20 year old technology. I have been using a $50 mummy sleeping bag I purchased on Amazon in below freezing temperatures with excellent results. Overall I think a small packing mummy style bag would be best for a bicycle tour.