jennycola, how much "brown sauce" is called for? If it’s only a little tiny amount, it might be Kitchen Bouquet? Although I’ve never heard of that going in chili. You should ask the chef. I’m sure it’s something not used regularly in home cooking. The chef should have known that and given you another option…but…
Here’s a recipe I found for professional brown sauce – I guess it’s like your general "white sauce" – only it’s um, brown.