Well if you can't find one, you could take a 2AA TSP and replace the Kroll with a Mini-mag tail cap and replace the spring with a suitably sized conductive spacer to make it into a twist pack.
Alternatively, it would not be too difficult for one of the modders with a lathe on this forum to make up a plug out of aluminium or brass that would fit flush to the end of the battery compartment, or have an interesting lanyrad attachment point or.....if you can design it and pay for it, there's probably someone who can make it.