ECI clamp if we can still find one is about $150 or so 
BI clamp may be a little less, and it will not be a standard BI clamp 
as the ECI boom does not have the flats machined @ the end of the boom 
the clamp mouth is wider , the BI booms have flats (or square) machined on the boom clamp end
so the clamp mouth is narrower than the ECI clamp, the BI clamp is by far more beefy 
than the ECI clamp
Dan T