PDI (now trading under the name X-Fire) have a few new products out of interest (including a heap of new inner barrels). There’s a new Patriot style battery stock unit for the M16/4 series. Better yet it looks to be quick release, so allows easy battery swaps.
They also have instructions online that show how the kit fits to the standard TM AEG, and how the electrics need to be reorganised. The kit retails at 7,800Yen