I can build a device that will disable a significant number of wireless alarms on the market in the UK. It costs about £12 to make. It took very little research (relatively) to work it out.
Never seen anyone else sell them - I've even tried asking on some of the forums that are used for trading ATM skimmers, fake chip&pin terminals etc. They just aren't made - criminals aren't currently interested in bypassing alarms on domestic properties.