From the pictures it looks like an ordinary metal box from RS Components or Maplin, and it would appear that you alter the desired wheelie angle very crudely by turning the whole shebang to the desired mark on it's backing plate.
All this suggests that all the box contains is a cheap tilt switch that you can get for a couple of quid from
HERE Couple that with the cost of the box and another cheap switch to bypass it and the whole lot would cost you about £20 to make tops