売り切れ

How it works

すみません (sorry) opens the sentence as a soft apology before delivering bad news — it's actually a frozen polite-negative form, so you use it as a set phrase. After the comma there's no subject or topic at all; context (the thing being asked about) carries it, and 売り切れ(うりきれ) (sold out) stands alone as the description. The polite です (is) closes it, keeping the whole reply courteous.