As for pads, I never use HH brake pads, but I also never play games on the bike...
There used to be a list of calipers from other bikes that can be used on the zg1000, but I think that may have disappeared when the old forum went away a year and a half ago...
Ever ran stock pads? If so then you've run HH pads; or at least Big K's version of them.
As I commented above there is no other brake caliper that is any better that will "simply bolt" on; and sadly at this time no one is making adapters. I'm not complaining but it takes a lot of time, effort and investment of money to offer upgrades to a diminishing market; ask me how well I know.