I rate the Joseph Kousac ones (no idea if available in NZ!), and find they are both larger diameter (better rolling) and narrower in width which gives that little bit of extra space for your shoes/heals. I think SON do a very similar set which might be more widely available through SON dealers?
Is there a go to EZ wheel kit from the after market? Brompton genuine parts a bit few and far between here in NZ.
Also are they actually lower profile and they stop you shredding your ankles? Asking for a friend