After two years of service my HO 3 truck Shay has cracked a gear. It is in the middle truck and despite it now driving only half of the middle truck the Shay runs well. I would happily purchase a new middle truck assembly but your parts people tell me they can't seem to get the Chinese to send them a supply. It still runs so I'm not taking it out of service just yet- any idea when/if those trucks will be available again?