Yes, i understand. I think the best way is go for Chris Church battery box and Y cable with 4.7k mod. Y cable should have 2 mini xlr inputs (for your mics) and output one mini stereo jack (for battery box). Then you will connect - Mics -> Y cable with 4.7 mod -> Battery box -> Ext in (Tascam). You can buy second Y cable without 4.7k mod for recording quiet acoustic shows, then you will use - Mics -> Y cable without 4.7 mod -> Battery box -> Ext in (tascam)
There are more info in the forum e.g. here
http://taperssection.com/index.php?topic=108196.0
or google this: 4.7 mod site:taperssection.com
Thanks for your suggestions but I really want to avoid extra leads. A simple plugin phantom power adaptor seems to suit my needs better.
Because of the gear you've bought, you are now trying to fit a round peg into a square hole. Unfortunately, while the adapter you're asking for is available, in my opinion that wouldn't be a very good option. See the last paragraph for details.
First of all, I agree with the other responses that you should buy a two wire battery box.
Most stereo microphones that use 9V power, also known as Plug In Power (PIP), terminate in a single 3.5mm stereo connector. If your mics were terminated similarly, you could use the Ext In connector on your DR100mkIII to power your mics.
However, since you have two mono microphones, you cannot connect your mics to the DR100mkIII, so I agree with the others that a two wire battery box is your best answer. They are tiny.
You also need the 4.7k mod if you'll be recording loud music...without this mod your mics are going to distort at high volumes. This is a very simple mod.
OK, so if you insist on the phantom power adapters, this is what you need to buy...
http://naiant.com/studio-electronics-products/inline-devices/pfa-phantom-power-adaptor/I'm going to be honest though that this would be a poor decision compared to the battery box. Read the reviews of the DR100mkIII from users that operate the DR100mkIII with phantom power turned on. Phantom decreases battery run-time on the DR100mkIII significantly. In my opinion, you'd be solving one problem and giving yourself another.
Battery boxes are very small compared the size of the DR100mkIII.
Finally, it's unfortunate that you've probably purchased the DR100mkIII because you mistakenly thought that you needed a recorder with two XLR connectors in order to connect your mics, but since you're a stealth taper, I would consider selling the DR100mkIII and buying a handheld recorder...and again use the battery box solution recommended above.