>>490246> a small, ultralight, ultraportable sleeping bag?I'd suggest that as you've got a bike, weight isn't an issue and thus you don't really need to go ultra light and should instead look for a sleeping bag that's warm and comfortable, yet sturdy.
I'd also say that if you don't have a tent or hammock, (and even if you do) you'll need a GoreTex bivy to protect the sleeping bag from getting wet, dirty and ripped up and Thermarest type sleeping pad, for padding and insulation.
So you might want to consider getting a G.I. milsurp sleeping bag, which has a heavy and a light bag, plus a waterproof bivy and can be had for under $150.
In warmer weather, you can sleep inside the light bag and on-top of the heavy bag for added padding and if it gets chilly, (as can happen even in summer) cocoon-up inside both bags.
