Proburger is an alternative to cheeseboroughs or mega-couplers. They have half couplers and snap couplers which are interesting alternatives. I particularly think that the snap couplers could be useful for rigging frames directly to battens. A black finish is also available. TMB also has a variety of other theatrical products.
Mega-Couplers have a wide range of products including one that threads directly to a pipe which is great for booms. You can check them out at the 2nd link below.