on this is to do it via the AD. I'm not sure a typical jeweler would be well equipped to do the water/pressure test to make sure the crystal is definitely air tight. Not to mention that the sapphire cyrstal is possibly thicker than the normal ones that you would find. OP/Richemont is centralizing all their service so they wouldn't sell/ship the part to any dealer anyway.
As gazoz mentioned, 4-6 week is really not that long of a wait and you have another Panerai to tie you over in the meantime? In the worst case, just buy another one to get thru this wait?