Hi guys,
As some of you know, I organized a group buy for the QS early this year - through MINI Madness. It was a very pleasant experience! As I've shared with others, If I were in the market again for another catback system, I'd get the QS again. I'll spare you the reasons as it sounds as though you guys are already sold on it
Group purchases since then have become more popular and seemingly more difficult as well. Both George and Randy have done quite a few of them, and at this point, as last expressed to me, they find it prudent to not do anymore.
It might be worth finding a newer company, looking for some exposure, who might be willing to roll with you guys on this. Maybe you have already tried this...
It looks as though I will be trying to sell mine as I attempt to make a new system this Fall/Winter. I expect to lose the cool looks and sound of the QS

I hope to gain a little more in performance and shed some more weight - mostlly through a battery box removal. I already have at least a couple guys lined-up who want the exhaust though
Have you tried Out Motoring yet?
http://outmotoring.com/quicksilver_s_exhaust.html
I forgot the guy's name, but someone from this company frequents MINI2. A really nice guy also! I'd inquire with him/them. And even companies that offer any products from QuickSilver or London Stainless should be considered - like the header. if approached, they might be willing to swing a deal for you guys.
Don't give-up!!!
Good luck.