I have to agree that unless most of the comics in your database include the barcode, a tool to bulk import by barcode would be of little help. For getting nearly all barcodes of *American* comics and trade paperbacks, at least, you could consider a partnership with Diamond Comic Distributors, Inc. (or in short: Diamond). They are the largest comic book distributor serving North America, and are known to have similar partnerships with other comic book collector software vendors.
I have to agree that unless most of the comics in your database include the barcode, a tool to bulk import by barcode would be of little help. For getting nearly all barcodes of *American* comics and trade paperbacks, at least, you could consider a partnership with Diamond Comic Distributors, Inc. (or in short: Diamond). They are the largest comic book distributor serving North America, and are known to have similar partnerships with other comic book collector software vendors.