Pretty simple, you will need a Schrader tyre valve like this A length of Silicone Vacuum Hose ID 3 mm OD 7 mm like this And a jubilee type clip, i used one of these, 7-9 mm Remove the rubber around the valve, i used a knife and finished off with a wire wheel, then remove the valve core and shorten the valve, blow out any fillings and replace the core Push the pipe onto the valve, i used a dab of glue to lubricate it and as added insurence Then crimp on the clip Job done Total cost is a couple of pounds
There was a bloke on here called Keith.H who was selling these, I bet you've upset his sales forecasts.