Hey bloke,
Depending whether you want new or used.
New, I would try Motobins or Motorworks in the UK. Krausers or "standard" Touring style. Exchange rate brings them in around A$430 to 630 plus postage. Both are easy to deal with and the stuff usually arrives in a week.
Used try anywhere here in Aust which service or break BMs. Motorworks also sell second hand parts, so worth a try there.
I phoned Motorworks recently and they are easy to deal with. Even though the time zone change is ten hours a gentle reminder of the recent heat wave will surely bring a smile.
Cheers, Burt.