Richard: 

Any of the Heil headsets with the appropriate KW keying cable should do the trick. 
I use the Heil Pro Micro Duel which has the HC-6 element. I key mine with a foot switch but it works just as well in VOX mode. 
Mine was 150CAN shipped to my door and this included the Yaesu 8 pin round kit, 124 before taxes and shipping. 
You could probably do allot better in the states. If your feeling generous, take a look at Radio Sport. 
These can run you in access of 199USD plus the cost of cables. 

HTH and 73: 
Mike VO1AX 

PS 
You could also mess around with adapting computer chat headsets if you want to build a power box. At the end of the day though, get a Heil.