Often times there is a thin line between a binder and a filler...You might try mayo -- homemade is less noticeable -- Mustard --- Mashed Potato --- Pureed potato --- Sour Cream --- Crushed, (In a food processor) Ritz Crackers...Only enough of any of them, or a combination to bind the cakes together....After forming refrigerate for 15-20 minutes before cooking....HTH