Dave here is a list of places to get clamps:
Precision Metal Machining
3156-A Fitzgerald Rd
Rancho Cordova, California
Web Site: www.precisionmetalmachining.com
Note: You have to call them for the products they do not advertise them on there wed site
White Lake Marine
Web Site: www.whitelake.com
Note: Click on the tower speaker link. It will take you to the link to get the clamps.
The Speaker Can mating surface is machined with a radius for 2” 6” 8” or 10” Speaker Cans, or also available flat for box style speakers. Standard Tubing Sizes: 1.50" 1.62" 1.75" 1.87" 2.00" 2.25" www.wakeproducts.com
And last www.wakeair.com
Hope this is enough info.
these are listed in my how to manual, thats where all the info came from.