try mothers work - we got ours there, but it was about 4 mths ago and we bought the last one. I've been back since but they're waiting for new summer stock to arrive in from Australia (it was aussie brand). could be worth trying now......
ps. i do recommend a sleeping bag - really does help control the excessive wriggles and you know that the baby won't get a chill from the aircon, and it becomes part of the bedtime routine - our girl (now 1) gets so excited just to hear the zipper going up - knows it's bed time!