Someone once told me the outdoor market at 97th and Amsterdam during the summer used to have it. I never checked, even though I have carried a frozen one back in my suitacase from 450 miles north of Minneapolis, I love it so much.
Thanks for the suggestion. I should have been clearer, I'm sorry: I am looking for a restaurant in NYC that serves walleye. I know there are sources where you can buy frozen walleye online - let me know if you're interested.