I concur with those who suggest a light-to-medium weight sleeping bag. As an FYI - in the UK, Snugpak make an excellent bag called the "Jungle" Sleeping Bag on their MOD side and the "Traveller" Sleeping Bag on their commercials side. Identical bag - different colors.
Their MOD style uses Olive, Tan and Black colors. The commercial side uses brighter colors, like blue, red or green. It uses synthetic fill - easier to care for. This bag compresses to about the size of a pineapple, and weight less than a kilo.
Whatever brand or style you ultimately choose, any bag should have a completely zip around feature, so you can use the open bag as a quilt - either over two people or as a loose covering.
Some folks expressly look for
hiking quilts. These are semi or rectangular bags that are not as shape conforming as semi or regular mummy bags, but which open completely. They are intended for car camping - not necessarily hiking. While they do tend to be more spacious, they can be found with down filling. This reduces the weight and compressed size.
I originally used the Snugpak bag, then obtained the Alps Mountaineering liner for warmer months, and a Sea to Summit quilt for colder months. When home, the Sea to Summit quilt can be used as a duvet filler on my bed. I find this more versatile than a conventional sleeping bag. But everyone is different.
A liner is not completely wasted. I carry a rectangular microfiber liner I obtained from Alps Mountaineering. Check out their sleeping bag, quilt and liner range here. The prices are very reasonable, but they are loicate in the US.
Offering you high-quality design and construction at an irresistibly-affordable price.
alpsmountaineering.com
This is the liner I use and carry on every Camino. It compresses into a gallon (3 liter) sized ziplock bag and rides in the very bottom of my rucksack - just in case. I got the poly fiber model as it is more durable and slightly warmer. This liner is also available in microfleece, but that version is bulkier.
Oversized sleeping bag liner
alpsmountaineering.com
Hope this helps.
Tom
Hope this helps.
Tom