Where can I buy a battery operated horn to get an old twin-shock through an MOT. I'm told that the rubber bulb type isn't acceptable.

All you need is a electronic buzzer about a quid from a electronics shop ( get the loudest you can )

Just had a look. This will do the job its from maplin electronics. Hope this helps.

I got one from a local car accessories shop, just bolts on to the bars and buzzes when you hit the button.

I tried quite a few of the Maplins ones on my KTM 200 Enduro - but could not get enough volume - although the size and price of things was good!

Best bet I have found for trials machines - are the small battery ones sold in push bikes shops for around