Are they loose because the anti rattle springs (wavey thin washers) have broken? this is what happened on my SV discs, so I bought a new set from stealth products (
http://www.stealthproducts.co.uk/ ). You get new rivets (or bobbins as some people call them) new anti rattle washers and circlips to retain them, so you don't need any special tools (other than circlip pliers) or engineering skills to fit them. I ground off the swaged over part of the old rivet with an angle grinder and punched them out with a pin punch then reassemled with the new parts - all done in a hour or so. They cost £2.99 each rivet plus £6.95 P&P. Not cheap I know, but a lot cheaper than new discs and buying secondhand from Ebay is a lottery; so if your discs are good other than this it might be worth a try.