I went with a Chinese knock off from Amazon for about 1/2 the price Honda wanted. It fit perfectly just like the factory one and no drilling. It's level with the seat which makes a large platform for the Drybag and tent.
For some reason the link got altered after attaching it here. You can search XMT-Moto Rear Carrier Rack fits for Honda GL1800 Gold Wing 2018,Matte Black
Sold by: XMT-MOTO
$139.77


For some reason the link got altered after attaching it here. You can search XMT-Moto Rear Carrier Rack fits for Honda GL1800 Gold Wing 2018,Matte Black
Sold by: XMT-MOTO
$139.77


. They seem to be the go to paint company...might be worth dropping them a line. Failing that I suppose an enquiry via a Honda dealer might be another avenue.