I don't think I've ever used one. Neat adapter, but I've always just cut a cable and installed the latest connector of choice. Up-side is one less set of contact surfaces to complicate an issue. Seems like every adapter I've used sooner or later looses contact, particularly stereo gimmes. Down-side is my mike, etc. cables keep getting shorter.
Seriously, if you do buy a lifetime supply, then you can be one of the eBay suppliers.