I tried to disassemble my 0-6-0 for cleaning and a lube job. One cylinder broke off, so I ordered these from Bachmann:

http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_68_155&products_id=866

They have a few more rods on than the originals, but I would have to remove the old rods from the drivers first. Is that a pin holding the rods on or a screw? The head is round.