I tried to get one, ordering through Rakuten but no luck, the Japanese guard them like it was a vaccine for covid. Would be nice to fly with some accessories and stay under 250g...good luck with your search.
Nope it is not possible to just connect +§- to the DJI connector... There needs to be a BMS to feed the ESC board with voltage current and other parameters to allow the MM to start...
This is why I designed my B0B board (search it in the mods forums here). It could obviouly be attached to a LiPo batt if you really want to fly light ...