Here are some ways to translate it in English depending on the context:
* If it's not there: This is a direct translation and works in many cases.
* If it's unavailable: This is a more formal and polite way to say it.
* If you can't find it: This is more specific and indicates a search for something.
* If you don't have it: This is used when referring to a specific item.
It's important to consider the whole sentence to determine the best English translation.
For example, if you see "Si no está, llama más tarde," the best translation would be "If they're not there, call back later."