I think the shrimp (or even scallops) can replace oysters in this sandwich. The tartar sauce for the sandwich is included but you can easily use your own favorite store tartar sauce instead. Recipe source: Bon Appetit (August 1990)
To make the tartar sauce: (see note above for short cut) Place yolks (or egg beaters), 1 tablespoon oil, lemon juice, mustard and cayenne in food processor or blender and blend or process to combine. With machine running add the remaining oil (7 tablespoons) and process until thick. Transfer tartar sauce to a small bowl and stir in remaining sauce ingredients (green onions - salt. (*sauce can be prepared two days ahead and refrigerated).
To prepare bread for sandwiches: using a long serrated knife, cut loaves in half length-wise. Remove centers from each half, leaving a 1-inch shell. Place bread centers in clean processor or blender and using on/off turns, process until crumbs are fine. Transfer to pie dish or medium bowl and stir in dry breadcrumbs.
To prepare oysters: set up three pie dishes or bowls for dipping. Pie dish 1: whisk eggs and milk together in dish, set aside. Pie dish 2: pour in flour and set aside. Pie dish 3: bread crumbs.
Season oysters with salt and pepper and then dredge in flour, patting off excess, dip in egg mixture and then roll in the breadcrumbs. Repeat for all oysters (or see note above and use other or a combination of shell fish) and then refrigerate for 20-30 minutes.
Preheat oven to 350°F.
Place bread halves on cookie sheet and bake for 15 minutes or until golden brown.
Heat oil in skillet or deep fryer to 375°F.
Deep fry oysters in batches until crisp and golden brown, turning occasionally (3-5 minutes). Remove with slotted spoon and drain on paper towels.
To make sandwiches: spread the tartar sauce (see note above in description) on insides of each bread half, sprinkle with lettuce over the bottom halves and then top with tomato slices and finally top with oysters. Cover loaves with top halves of the bread. Cut each loaf into thirds.