Alternate seafood for etouffee
Shellfish is expected in etouffee, most commonly shrimp or crawfish. Crab meat is another option. Without shellfish it kind of isn't etouffee anymore, but it can still be great and you can still call it etouffee if you want!

For example, here's a recipe for chicken etouffee.

Where do you live that you can't find raw shrimp? I admire your gumption trying to make it with cooked shrimp, but I'm not surprised that it turned out bland and rubbery. Your best bet for raw shrimp is to look for it frozen. Many places will carry raw shrimp individually-quick-frozen and easy-peel, which means that the shrimp are already deveined, and since the shells are already cut down the back, they just pull off. An advantage of buying shrimp this way is that you can simmer the shells for a few minutes and get a nice shrimp broth to use in the etouffee sauce. Most markets that sell raw shrimp at the seafood counter are selling frozen shrimp that they have defrosted, so buying it frozen is actually a better option for freshness.

Since the seafood in etouffee is generally added last and just cooked through, you can really use whatever protein you want. Certainly whitefish would work, so would scallops. I once had a great lobster etouffee. Another great option would be to use andouille or kielbasa sausage with or without seafood too.