EX3 DC Plug Specs
 

I'm making a custom cable to power my EX3 through the DC input. Some googling leads me to believe I need an EIAJ04 plug and the centre pin is positive.

Can anyone confirm or deny this? Thanks!

Cannot confirm or deny... but this cable can be useful:
4-pin XLR to DC adapter cable for PMW-EX1/PMW-EX3

Thanks, I've seen that one too. Mine needs to be much shorter to a Switchcraft 761K. I have a funky setup on my Flyer-LE.

You are correct. I managed to buy a quantity of them from a local supplier so they're nothing too hard to track down. However the ones I have are not right angle entry. You may be able to buy RA ones but they'll most likely be already molded onto a cable.
There are some types of solder on connectors available in R.A. but such small sized R.A. plugs never seem overly successful to me.

Thanks, I think I've found just the thing from wagner.net.au, the MP204RA, right angle solder. $1.75AU each. farnell.com list the same thing as MP-204L.