Find a New Orleans deli that serves Chinese food, and likely as not you'll find yat ka mein. You might see it rendered yet ca mein, yakamein, ya ka mein, or under some similar moniker, and prepared in as many varieties as there are spellings (which I haven't exhausted here). This black-peppery version (small, $3.49) added pork and baby shrimp to the standard hardboiled egg and ramen-style noodles. St. Vincent is staffed by Chinese speakers (probably late of Vietnam, judging only by some of the groceries), but yat ka mein was absorbed into the city's black culinary vernacular long ago. On the menu board, you'll find it listed between egg drop soup and gumbo.
Update, January 2015: After a change of ownership, St. Vincent still offers po-boys, but the yakamein is 86'ed.
St. Vincent Supermarket
2372 Constance St. (at 1st St.), New Orleans