Get the 2pin and the HXT and solder away:
This one, I suspect from Jaycar CAT.NO: PS2014 $2.95
https://www.jaycar.com.au/2-pin-line...ector/p/PS2014
and the HXT 4.0mm is available on eBay, possibly now even from Jaycar or Altronics.
Or you could butcher your existing lead and just get the HXT 4.0mm plug and solder
or maybe it's a ec3 or ec5 available from Jaycar. There are several sizes of these new type battery plugs. It would be best to go and eyeball them.
Best
JA