A common expression in Portuguese is "isso" (pronounced eeee-so), literally meaning "this" and used with the exact connotation you've used it. Usually the speaker overemphasizes the stress on the "i", and the intended sentiment is conveyed very strongly, even when the recipient is a non-native speaker such as myself.

From a purely denotational perspective, the equivalent in English makes sense. However, when I read it to myself in my head, it just doesn't feel right. You can't modulate the pronunciation of "this" in any way to convey the same connotation. As is it looks and feels silly.

I'll stick to the standard English translation, "Exactly!", at least until people adopt the Portuguese, "Isso!" (which we all should, it's just so fun to say and perfect for the situation. Try saying it. eeeeeeee-so!)