Suedecloth is a good non-slip backing. I use poly batting just cos it's not important for it to be a natural fibre in a buggy and it's cheaper. I got a bit of that ready-quilted stuff for my latest one. FOE makes a good binding if you don't stretch it (the wide stuff). I've used quilting cotton to top them. I've also made a buggy sleeping bag from minky. That was nice and snuggly but I don't think I'd use it just for a liner. You can cut a vertical slot for shoulder straps if you want to be able to move positions. FOE looks good for binding the slots, too.
WAHM to Braden (5/05), Rosalia (6/08), and
Cosy Bundles sleep sacks now at http://bebezalicobber.wordpress.com/sleeping-bags/
Patterns available: one-size pockets (original and Tiny Tuck-in) and small velcro pocket - email me at estherk @actrix.co.nz