another kiwi here, my list of locals is mostly of operators willing to deal with me buying hobbyist quantities, as this is when the international shipping really bites.
+1 AFWE being a go-to, they’re always very reasonable with me, and I’m usually buying an annoying list of short cuts 800-300mm.
racetech (also mentioned above) in Aussie also keep aero / streamline profile 4130 in stock and have been happy to sell me cuts as short as 300mm for no extra charges.
Worth noting hillbrick also have good systems for delivering to NZ, I’ve found its always worth the phone-call, helpful service, heaps of knowledge means they can often offer a good alternative if something is out of stock.
Zipp plumbing plus keep easyflo flux paste and BOC prosilver45 (45%Ag) in stock, and are happy to sell it by the stick at trade price. the part number for a single stick of the silver is LTAT4563.
about a year ago I priced out what we were paying for argon through BOC at my workplace, and what it would cost for us to run double bottles from them to avoid downtime, and based on going through an F size bottle once every three to four weeks it was notably cheaper (and more convenient) to get two D size bottles from Bunnings. also worth considering they’re open till 7pm, and on Sundays.
ill throw steel cuts.co.nz on the mix too; often WAY more expensive than other sources, however, NZ based, fast shippers, (mine usually ships before i’ve paid the invoice, despite it being a cash sale) and happy to sell short cuts down to 30cm, so can be a lifesaver if you need one or two tubes.
Issac Woodbridge at Woodbridge industries in Petone is a tube bending and forming wizard. he usually works in stainless and mild steel , but has been happy to work with 4130 i’ve supplied whenever ive needed something I couldn’t pull off myself. (for example, 250mm CLR, 45deg bends in 1 3/4" downtubes, required filling with serrobend and section rolling, or oval profile bends for fancy seat tubes which follow the tyre OD’s on tucked track bikes. etc)
lastly, there’s a stash of straight gauge 4130 tube, aswell a range of sheet, owned by the vintage aviator in wellington, who as a company, seem to have all but disappeared following recent controversies. but the tubing still exists there, and whenever i’ve asked the guys I know with links back to TVA if I could buy small amounts ( 1-2m) its been easy. they seem to have a wider range of thinner wall sizes, especially in small stuff <1" OD than other kiwi outfits.