I have the SMDV Speedbox Flip 24, which is quick to set up and fits the Godox V1 perfectly.

Alternatively, the Bowens Adapter S2 and any Bowens Mount Softbox up to approx. 90cm. Larger makes no sense. SMDV is also available with Bowens Mount. They are really top quality and quick to set up. Many cheap softboxes can't even be folded up. So watch out.

Godox S2 System Flash Adapter Bowens Mount (bracket)