Tutter, am also swaddling my DS2, also large and strong - he is in 6-9 month clothes and only 3.5 months old!!
I use a square cotton jersey blanket which I bought for DS1 ages ago in Mothercare. Its the best thing I have used, its thin and stretchy and he cant get loose in it. Any good size stretchy blanket should do. Can you go shopping? I think its easier to judge if you can have a feel of the fabric, rather than buying on line.
Yes - its lush - found them at the baby show last year - such cool stuff - have the bib/burp cloth sets, swaddle blankets and some of the katvig clothes. They do have sales and they do offers at the baby shows.