I'm in urgent need of an altimeter for a range of 30-40 meters with an accuracy of +/- 1 foot.

On reading up a bit, i found that a LASER altimeter fits the criteria. But its too expensive and a very few companies offering it. Please suggest some light weight altimeters(around 200g) with very high accuracy for the said range. Pressure altimeters do not serve the purpose due to insufficient pressure changes at such low altitudes.