Don't drop your GTR - if you do the mirrors will almost certainly suffer.
Second hand mirrors are like gold dust. If you have any to sell, please let me know and I'll list them on the "for sale" page.
I have heard that the mirrors from a Bedford Rascal will fit the GTR and they are much cheaper and easier to find. If anyone tries these out and they work, please let me know and I'll add the comment here.