drophead banner by Randy George, on Flickr
Drophead Speed Equipment
http://www.drophead.co.jp/
Basically a parts dealer for everything that is Roadster related in Japan, they also sell/source parts for vintage motorcycles as well.
I used to buy a bunch of items from him back in the late 90's through early 00's but later his site disappeared.
Toshitaka Masugata-san is very helpful too, just send him an email.
They still make their NA and NB exhausts!
NA version
NB version
But sadly Drophead no longer makes the radio/gauge dash panels
Lucky for me I still have a new one still in the bubble wrap that I bought 6 years ago
But I think DDM Works here in the USA still sells them as well?
Here is my Drophead version though.