ok..... as i ran a chandlery I can tell you there hard to find... sorta I don't know which area of NZ your in but here goes.... nuts 1/4" if in Auckland go to iether fosters there at the bottom of victoria st from mem.... search harken fosters or forster harken also in glenfield you have chatfield eng they make those sorta things.... oh in westhaven if you head into sailors corner before I left we had some 1/4" strut bolts allsorts with some loose nuts e.c.t if your after a few there may be some loose ones that they may sell if you head in there check theres not a vrod parked round the side if there is look for the older guy with the gray beard he's into bikes e.c.t and say rob told you to come and see him.
as to the brass plate that stuff is hens teeth there is a company that advertises in the shed mag called small metals company or something like that they sell small bits of brass stock e.c.t for model engineers and such forth.
hope that helps.