I would suggest trying the sweater sock or having one of our talented seamstresses here on YT custom-make you something. Riley was 1.4 lbs when we brought her home at 11.5 weeks, and everything was too big. Even PetSmart's XXS sweaters! I didn't know about the sweater socks then and wish now that I had.
Jodie (
SissyAngelWear) made Riley a custom nightie that fit her tiny, tiny size. It helped to keep her warm since that was a factor with her being so small.
Here's a pic.
And Des with
GoFetch made a custom T0 harness for her as well.
Here's a pic.
Can't wait to see pictures of your little one!!!