New look pattern # 6525...although large is up to 11kgs...so you may need to get a bigger pattern. I made my DS 2 x all in ones when newborn....put a zipper down the front instead of snap buttons etc at crotch.

Why dont you make some flanno pj pants....and buy a long sleeve white top - thats what i did for my girls. White top only cost $4.99 from bigw, then i did some applique, and sewed some of the design from the flanno pants, onto the centre of the white top....they turned out unreal.
Just a suggestion...
GL.