There have been a few threads on here from us Kiwis.
My dad built an LR3 recently using stainless 25.4mm x 2mm tube from Industrial Tube in Hamilton. For shipping you can get them to cut it down to a size that’ll go on a courier and it’ll end up cheaper.
NZ Steel and Tube was another option that seemed decent.
Ultimately you’ll probably need to be dealing with metal suppliers rather than Bunnings/Mitre10 so it’s a bit more legwork, but well worth it. If there’s a local steel supplier you could always give them a ring and explain what you’re looking for and if they have any suggestions. The stainless tube from Industrial Tube in Hamilton was dairy grade but with cosmetic blemishes from the welding, so basically a ‘byproduct’ so cheap for the size/weight/finish etc.
For my MPCNC build I used 25mm OD aluminium extrusion but that was from the before-times when 25.4mm wasn’t an option yet.
Also, as a word of warning, if you buy 25mm make sure you check the actual outer dimension before getting too caught up printing parts. Tons of places advertise 25mm tube that’s actually 25.4mm/1" nominal tube. There are also a bunch of tube standards that specify based on the internal diameter which can get confusing.
Sing out if you get stuck, I’m sure we can help.