Have 2 of these spare routers running OpenWRT, was using them in China to tunnel traffic to my VPS in L.A, they have US power bricks but the voltage is universal so you can use a cheap pass through adapter or a plug from a standard router should work fine too (12v/3.5A).

https://www.netgear.com/support/product/WNDR3800
https://wiki.openwrt.org/toh/netgear/wndr3800

CPU: Atheros AR7161 rev 2 680MHz
Ram: 128MiB
Flash: 16MiB
Network: 1 WAN + 4x LAN (GBit)
Wireless: 2.4/5GHz
USB: 1x2.0

Using the build from here https://forum.openwrt.org/viewtopic.php?id=28392 but of course you can compile your own, this is the WNDR3800CH which is hardware identical to the standard WNDR3800 but the stock firmware is for Charter customers.

These are scuffed a bit on the top but functionally working perfect.

Looking for 40$ each shipped. Could do pick up in Wellington but won't be there until the 13th.