Derek,
No, I can’t find one either, but throughout my research I have learned quite a bit about this instrument. Martin discontinued the B5-40 due to the neck design, it could not withstand the stress of the five strings when used in a professional manner, the keyword word here is “professional”. It’s not a problem if you play it a couple of hours a week around the house. But when you are gigging, moving it around, performing 3-4 hours a night, 3 to 5 nights a week the tremendous stress from the fifth string was too much for the neck, they had many complaints from professional players, that is why there was only 54 of them made. I just don’t think, they think, the market is big enough to invest the time in the re-design, especially with the trend of bass players is going back to 4 strings. Good luck ~ Chris
