It been out of production forever. E-Bay, Racejunk or they turn up occasionally here but they have got stupid $$$.

I have seen NOS ones listed for $1500.00 and they seem to be in the $700-$800 range used on average.

Here's a link to Don Dulmage's website where he fabbed a 2x4 top for it.

http://www3.sympatico.ca/big-d/2X4.htm

Kevin