Nick, Lencarta do some really nice "octoboxes". That would be my first port of call.
I have the lencarta stripbox and is of very good quality, for an octobox I bought the Phot R one and that seems to have held up so far..
https://www.amazon.co.uk/Professional-38-Inch-Octagon-Reflector-Honeycomb/dp/B00VHVOUPW
Phot-R Professional 95 cm/38-Inch Octagon Softbox: Amazon.co.uk ...