I am going to make some natural sleeping bags for my bub - I have a simple sleeveless Burda pattern and instead of poly batting (as in many of the commercial brands and as recommended in the pattern) am aiming to use wool batting (from my local quilt shop) or a cotton batting that has been fire retardant sprayed that I will need to order off the net (remember 100% cotton fabrics tend to have a high fire danger so also be careful what outer fabrics you choose). I think it would be difficult to find a soft wool jersey (aka the merinokids bags) and if you did, it would probably be expensive so best bet would be to buy a pattern that makes the bag liek a quilted one and use a natural batting. I have a pattern for the fleece bags too (single layer of fabric) but am making those with the pram slit for next winter as the fleece is fine when out in the cold air. In bed it would probably sweat alot and I am not fond of unnatural fibres in bedding due to the SIDS risk being increased in winter with overheating. (My nephew died of SIDS which lead me to look at all the stats and more babies die in winter due to being too rugged up - synthetic fabrics don't breathe like natural ones so they will always be my preference in the cot).