Crapvendor emeritus Brando is selling a new "Hand-held portable universal cell phone jammer" that works on a variety of frequencies (although likely not all at once) and is almost certainly illegal to own or operate in the United States. With its battery fully charged it can blocked phones in an eight- to ten-meter range for around 90 minutes. That won't ensure you a quiet theater, but you might be able to silence your corner bar.
It's $250, plus shipping.
Product Page [Gadget.Brando.com.hk]