Without knowing the specifics of what you're looking for, it's difficult to point you at any one tool or even a set of tools. It really depends on what you're looking to find. Most tools concentrate on a given class of data, such as credit card numbers for PCI compliance.
However, one thing to remember about generic searches is that it almost always boils down to looking for a signature of some type. So even if there isn't a tool that covers what you need, if you can figure out a pattern to what your seeking, then you may be able to write a script that will automate your search across multiple boxes using that pattern. For a simple example, consider that US Social Security numbers are 9 digits long, and are usually expressed in this format: NNN-NN-NNNN. If you were seeking SSN's then the script would have to search for strings of 9 digits without the dashes, and in the format with the dashes; to cover storage of either the common format or one that is reduced to just numerals.
Feed your script a list of boxes, and it would log onto a box, do a search, log the results, and move on the next box. After that, all you have to do is look at the log file. Sure, it might miss data that was formatted oddly, but it would get most of the data that might have been compromised by a sloppy user, or one with evil intent.
The same principle could be applied to a search for credit card numbers, or keyword search for specific proprietary data. Just remember that the more specific you are about the "signature", that the less false positives, but you may miss data that is formatted oddly or misspelled.