The recipe for Japanese Curry Rice comes from Marc Matsumoto of norecipes.com. He says: “ I make almost everything I post without a recipe. I think cooking is most fun and innovative when you just wing it. I do recognize that not everyone is as adventurous as me, so I post the ingredients and method to give you a starting point.”
So in that spirit, substitute okra for the carrots, thinly sliced green beans for the peas, use applesauce instead of the fresh apple, or make any other substitutions that appeal to you.. You could skip the protein and still have a lovely meal.