I buy most of my stuff from the states - better variety of just about anything. Other may correct me but if it was me I'd be starting with a new pair of discs, new pads and a left caliper. Master cylinder may also need upgrading. Most stuff that fits the 900SS should also be right for you. Watch the disc offset (how much it sticks out from the wheel) and if you fork is standard, the bolt spacing for the brake caliper. If it's old like might it will be 40 mm bolt spacing and I think 10 mm offset for the disc.
If you buy from overseas just watch how much it totals as I have gone over $1000 Aussie once so far and had to pay import duty and GST. They work it out on the exchange rate the day they get the paperwork so if you have to buy in a couple of shipments a month apart you will still be in front.
sell discs, calipers and lines but don't show very many master cylinders. A Motowheels dude is one here at times and he may be able to put a full or part package together. They are also a sponsor of this forum.
I bought a stainless braided clutch line from Hel Performance in Qld and was impressed with the service http://www.helperformance.com.au/
I placed my original order for it in the USA and it was redirected to Aust. Got an email from them and they also phoned to make sure they made it with the ends at the right angles. My brake lines I bought off eBay - UK I think.
Last thing is, I think with some sites, I had to copy and send a part of a bank statement that had the number and address to verify that the sale was legit.