Transfer Apps to Mobile Applications at the same computer again

Hi all,

I used to stored the iTunes Media content at a removable USB hard drive. However, the hard drive recently crashed and I have to reformat the drive.

I can restore almost everything to the iTunes directory except some IOS Apps, which I can no longer find them in the AppStore as the publisher closed business. As a result, in the "Apps" tab, those apps are marked with "!" and iTunes cannot locate the physical file at the file system. For other apps, I used a manual way to download those apps from the AppStore again to make them available at the "Apps" tab.

I tried "Transfer purchase", but those apps wouldn't extract from the iPad to my computer again. I tried de-authorize and authorize the computer again, yet not luck still.

I wonder there is any way to extract those apps again from my iPad back to my computer so that a proper backup of those Apps are available again.

Thanks.