Most of the tanks on e-bay or from UK or US suppliers are from India, Paskistan or Afghanistan. They vary in price, quality of chrome and workmanship. There are several threads on this forum and other forums with testimonials. http://www.britbike.com/forums/ubbthread...true#Post341259
and more (use the advanced search feature of this forum).
I recently bought an Indian made plain chrome tank from S&M Motor Company through E-bay so I could return it and was protected (ha!) through e-bay and Paypal. It is OK, they are a sponsor here, but I personally will not do business with them after the sent me a seat completely different than one pictured on their auction. Fought to get my money back, but am stilled pissed and ended up buying a Leighton seat kit.
You will generally get what you pay for if you order from overseas on E-bay. Buy a higher priced one with many good feedbacks. Shipping may take a while and if there is a problem it will take longer to return or repair.
Ross Thompson does magic with damaged OEM tanks, but quality comes with a price. http://www.execulink.com/~rosst/
Evan Wilcox makes beautiful pieces of functional alloy art at a premium price. http://www.wilcoxmetal.com/other.htm
The Tank Shop's waiting list is longer than he will quote you.
TAB II are making tanks again http://www.tabaker.co.uk/TABWSITE/UK.html
Consider the tanks from Burton Bike Bits. http://www.burtonbikebits.net/Tanks.htm
I hope this helps you in your decision.