Does anyone know where I can buy Katsu Curry sauce?

Katsu Curry sauce is not a brand, but rather any Japanese curry sauce used in the making of the Katsu curry recipe. According to many sites with recipes for katsu curry, the sauce should be one that has a sweetness, it should be fairly mild and should not clash with the other ingredients in this delicious dish.

Typically, the recipe is made with chicken.

Of course, there are many sauces you could chose when making this recipe.
Rowena's Gourmet Curry Sauce is a great choice, at a little over $6 a jar. This is an excellent sauce to sauté with. It's superb on chicken or shrimp on the grill. Whether you spoon it over cream cheese topped with chopped dried fruit or add it to hot macaroni noodles, you'll love this sauce. You might also like the Curry Simple  Mango Stir Fry Sauce, which  is a light balance of sweet, spicy and mango flavors. Great for stir frying chicken, shrimp, fish or tofu - it also makes a wonderful dipping sauce for appetizers or can be used as a marinade.
Golden Curry Sauce Mix Japanese Style 8.4 Oz Medium Hot Traditional is a Japanese curry sauce mix. A long-time seller in Japan and thebest selling curry sauce mix in the USA, its best harmony of spices and herbs has set the standard of Japanese style curry.