Prior to spending your hard earned money so quite a bit of research as there are several types of brackets, hot shoe extenders, on the market.
Try: Markertek.com
B&H pro audio division/accessories
Any of the sound pro distributors in California and also many of the aftermarket accessorie stores listed in the back of magazines like VIDEOMAKER.
I have several types and styles of brackets that I've bought that I use depending on the application of accessories.