I just checked bikebandit.com for you but unfortunatly they are in the states and they didn't have a 2006 650. I would try the wreckers first just to see if you luck out, it's a fairly new bike still unfortunatly so it may be hard. Try and look to see if another year will fit. Just based on the styling maybe a 2007 bandit 650 or 1250 may work? Although they are fuel injected and I'm not sure if the fuel pump is in the tank or on the throttle bodies. I'll try and figure it out for you.
Well the good thing is I don't think the 1250 has the fuel pump on the tank however I don't see any sort or petcock as the fuel pump handles fuel delivery to the injectors. Here is a schematic of a 2007 bandit 1250 fuel tank.
http://www.bikebandit.com/2007-suzuki-gsf1250sa-bandit/o/m17390#sch554071Here is a schematic of a 2005 Bandit 1200 (my bike) for comparison:
http://www.bikebandit.com/2005-suzuki-gsf1200-s-z-bandit/o/m17389#sch553917Maybe one would work? I know that the 2006 is the odd ball of the entire bandit line it was only made one year and it was a hybrid of the fuel injected models styling with the old engine carb set up. While it looks very sharp, getting parts may be problematic. What does the dealer want for a new tank? Or does the tank actually function but is cosmetically damaged, ie scratched paint, dented, etc. It may actually be cheaper to fix and repaint the tank then order the decals then to buy a new tank.
K found what looks like to be a european site, here is your microfiche for your tank. You can probably salvage the fuel cock.
http://www.bike-parts-suz.com/suzuki-recherche-bike-pieces_nn.php?compteur=1215&PartsListID=3571184676 Euro for a new one. Ouch. It will be slightly cheaper here but your still looking at 800 bucks probably at least. Its only a few hundred dollars to repaint if the tank still works.