Here is one from HK (no PVC) but same basically.
Originally Posted by Tony97
I will try to post a picture of my siren. It is basically a very small siren in a piece of PVC tube. It about 1/4" wide by 4" long tube. It has a servo plug on the end. It monitors a valid signal from the receiver. If I signal pulse is detected, the siren goes off. Once the pulse width is valid, it shuts off the siren. Very simple and these are commercially available.