Dunno about you, but I think most of the rear bike lights sold in NZ are rubbish. They all come with fittings to fit them to something round like a frame or a seat post, and there is hardly any choice about where to mount them, and I want mine on the back of my pannier rack. So we end up jerry-rigging some daft thing and our rear lights fall off and there goes another $25 we’ll never see again.
But after a bit of digging I found Cateye part CA5342250 and it looks like this:
It is within most NZ bike shop’s capabilities to order one in for you and that’s why I gave the part number above. It should cost about $10 or so, which isn’t much, except it is really only a small piece of plastic, 2 screws and 2 cable ties. The holes are 50 mm apart, and were easy to fit as my carrier had a metal plate hanging down with holes in the right places. See:
and now I can ride around with this without it falling out: