Bill, I assume you are talking about garmin BlueChart or Bluechart g2? Although no longer in production, about a year ago I was able to purchase
used off Ebay virtually all the additional charts
I wanted for my GPSmap 2010C and 3010 C, including US east coast
and the Chesepeake (even though I may not end up going to the latter, I fugured I may as well get one). It may take awhile for the one you need to be listed, but don't give up hope! Keep in mind that they will not be current
, but in conjunction with paper charts
and a laptop
below with up to date charts, it works for me.