What about buying a set of srew guages and matching one of the gauges to the threads of the bar and then purchasing a tap of the same guage. That way you should be able to SLOWLY tap past the bridge and into the block without dissassembly or altering the insrument in a discerable manner. Just go very ssssslllooowww and lubricate the tap and it shouldn't alter course too bad.
Of course doing this will leave you with an elliptical hole in the block, so you may want to fill the old section of the hole that is, hopefully, now vacated with a metalicized polymer like JB Weld to bring the hole back to being a secure fit for the arm. I would shoot a little JB in the hole and and then run the arm in to full depth AFTER COATING THE ARM WITH PARAFIN OR SILICONE SPRAY to keep from welding the arm in position.
On the other hand if the integrity of the instrument is paramount, sending it to fender is probably your best option.
hope this helps, Nate Robinson