If anyone is interested, these are Tyco/TE Type GET.64 connectors. The correct terminals are # 1393367-1 & 1-1419158-6 . As far as I know, you can only buy the terminals in bulk, and you'll need a high quality crimp tool that can do U-barrel type crimps in 22awg and smaller. Hispirish's method of harvesting the pre-cripmed terminals from JST connectors might be better for the hobbyist that does not have these tools or is inexperienced with crimping small u-barrel ends.
I'm most likely going to build a few of these Y-harnesses, but I don't have the housings yet, and I'm not sure what the rules are with regards to selling parts on the forum.