I had the same problem after cleaning out my freezer. TERRIBLE FISH ODOR! We tried the newspaper, coffee grinds, vanilla, bleach and baking soda. Nothing worked. I was ready to bring this 2 year old freezer to the dump just to get the smell out of my basement when i decided to give it one last try. I sprayed about 1/2 bottle of lysol mold and mildew spay all over the racks and coils, especially the tubes running down the back side. Then i got a kitchen bursh and scrubbed all the racks and coils and rinsed about three times with plain hot water. I even sprayed some down the drain tube and rinsed that. Well the smell is GONE!!! There must be something in that cleaner that neutralizes that fish smell. Good luck!!
Wear nose-guards.The smell is not as overwhelming as is the sentimental attachment. You are gonna have to spend some money irregardless. Get a chemist to diagnose the source of the obnoxia-olfactorio. Get to the common food spices section of your favorite supermarket.Purchase 3 spices that you enjoy the fragrance of. Rent or borrow a freezer compartment for 5 days. Empty all of those 3 containers into,hand rub,all about the insideAfter 5th day wipe inside out with dry clean cloths or paper towels.Hire one whom can construct an aluminum or stainless steel or both inner coat for your 'attachment'.Invite me and 3 guests of mine over for Bar-B-Q 5 weeks thereafter!