First let me say, l really love Huitrerie Regis. The location is perfect, the seating and the owner are perfect and the oysters are lovely. The only little issue l have is that at 24-34 euros/dozen for a variety of # 2's , l do not get to go too often. Walking with a leading Parisian Chowhound a few weeks ago, we came upon Huitres de Cancale on Rue Chabrol in the 10 Arrondisement, fittingly near Poissonniere Metro.
A shop sized even smaller than Huitrerie Regis, seating only 16 patrons on a small uninteresting street. The owner, waiter, shucker, cashier, and general bon vivant takes your order, shucks at will and serves your oysters with a basket of coarse bread, butter, and a lemon wedge. They were wonderful, cost 16 euros and at that price l will be there twice a week as long as they are open.
l have been there twice now and to watch this man do everything but sweep the floor is Chaplinesque and very charming. Hope to see some 'hounds there. One other reason to go onto Rue Chabrol is the wine shop Vigne en Ville, who is a vintner for various vignerons who are friends in the Loire and other smaller appelations. Prices are very, very reasonable and taste his wares before you buy to your delight. They only have about 35-40 different wines, but more than enough for me. If you get 6-12 or so they deliver also.