Not sure if this helps Billy.
the last link has a list of places with phone numbers....not
sure if all of them have the national pass, but it might be
worth calling around to listings in CT, RI, and MA to see if
they carry the passes before you show up to them.
https://www.nps.gov/caco/planyourvisit/fees.htm
https://store.usgs.gov/pass
https://store.usgs.gov/sites/default...suanceList.pdf
Also,
The closest national seashore beach from chatham is in
Eastham I believe. That will be at least a half hour drive
from chatham without traffic. I could be wrong about this though.