Unfortunately, I haven't found another option that works as well as bananas for this dessert. I've tested tofu and dates but neither worked. If you're worried about there being any banana flavor, you could omit one banana and use around 1/3 cup whipped coconut cream in its place - but then the pie will contain higher levels of fat and calories. I've used equal parts Greek yogurt and peanut butter (plus maple/honey) before, too, in a fridge-friendly version- but haven't tried it frozen.