If your in Truro, I think there is a ramp in the Pamet river.
I have fished from that river mouth along the shore towards the PATH near Wellfleet (an obvious path on land to the shore).
Got some decent blues there.
Or,
Look for the fleet in that area and Billingsgate shoal.
Or,
If the boat is big enough do the race point thing that Saltheart mentioned.
Don't know about charters.
Good Luck.
