Contact Pipe Welders in Ft. Lauderdale. They work with a few outrigger suppliers and can point you in the right direction. They've probably installed several thousand units. I took my Hatteras and Bertram to them.
I have always used Rupp outriggers. I think you will find Rupps on most of the big sport fish boats. Rupp is located in Stuart FL. & they have a web site. Check out the Jarett Bay web site. I bought Rupp riggers for my 42 Post there. They have several larger sets still (surplus) and I picked them up for about 40-50% off the selling price of most distributors. I was on the Jarett Bay site recently & saw they still had two pairs of triple spreader set ups for sale. Dave