We have in the past always used Blundstone for larger sizes and wide fitting option. Haven't had any need to use them recently.

Hey Genevieve, how large/wide do you require? Blundstone's largest size in gumboots is a 13UK/14US.
The largest safety workboots I know of available from NZ distributors is size 16UK/17US, although some brands offer a wider fit than others. Gumboots are available in 15UK/16US.
Happy to offer some suggestions if you PM me, probably against forum guidelines for me to list them here...?

Hi Genevieve, I had the same problem last year with trying to find safety gumboots that suited our Manufacturing guys feet. It certainly wasn't one size fits all. We tried on a LOT of different brands, sizes, shapes etc and FINALLY found some that were comfortable. We eventually went for a Redband gumboot and a Blundstone. But it did take a while to find ones that suited their feet. Thankfully I only had two people to purchase for. Good luck.