Make it yourself! Start with a real, whole coconut. Select one that feels heavy for its size and you can hear the 'milk' slosh around inside. Food Network has instructions for dealing with a coconut if you have never done so. Look for the coconut cake recipes of Alton Brown. He bakes it, then uses the electric drill to open the eyes to drain it. The baking helps loosen the meat from the shell so you can shred it.
Then you need to make decisions . . . a traditional coconut cake is a white cake, but white cakes tend to be drier than yellow cakes, so I use a yellow cake. I don't mess around with making a cake from scratch but just use a cake mix. I put a little coconut extract (yes, out of the McCormick's bottle) into the cake mix before baking.
When I shred my coconut, I go for longer shreds and can either use the shredder wheel of my food processor or pull out the old hand grater. Of course you took off the dark brown inner husk on the meat with your vegetable peeler. I then add a little powdered sugar to the shreds and a little of the coconut milk, put the whole thing in a zipper plastic bag so that I can shake it up from time to time and refrigerate it until I'm ready to use it.
Then you have decisions about the icing--at our house the preference is for a simple butter cream icing, though I think the more traditional is a 7 minute icing that requires cookig. In my butter cream I use the coconut extract again instead of vanilla.
I split the two layers once they have cooled so that I have a four layer cake. I usually add what coconut milk I have left to a can of coconut milk and moisten the layers before icing. A generous layer of butter cream goes between each layer, sprinkled with a good handful of fresh coconut. Plan ahead so you still have enough coconut for the top and sides. Don't mix the coconut into the icing but rather press it in once the icing is in place.
This is a cake that needs to be refrigerated and it is always at its best the day after making it.
Outside the freezer section with such paltry offerings as Pepperidge Farm's squares, coconut cake tends to be seasonal and available from bakeries during the Christmas holidays.