I have a Bachmann Spectrum Maryland & Pennsylvania 4-4-0 #4 which is DCC equipped. I also have a Bachmann Spectrum Maryland & Pennsylvania 4-4-0 #6 which is DCC and sound equipped. I love the sound on the #6 and would like to add sound to the #4. I have looked inside the tenders of both engines (which on the outside appear to be identical except for the numbers) and saw what appears to be a plug-n-play sound module and speaker in the #6. My question is simple, does Bachmann sell the plug-n-play sound unit and speaker (light steam) separately? If so, what are the part numbers and how do I order? If not, can anyone recommend where I could obtain a plug-n-play sound unit and speaker?