I use a cot bed as I don't back pack any more but before I stopped I used a thermarest with a cell foam mat on top. To stop it sliding off I put a bit of self adhesive Velcro on each corner of the mat and roll which did a great job of keeping them in place. There's no weight to speak of with a cell foam mat just a bit of bulk you can tie on your pack. Although no self inflater is really comfortable, combined with the mat they made for not a bad nights sleep and of course insulates you well from the cold ground (the Velcro idea works well with a mat in a bivy bag too).