As others have pointed out, it seems impossible to get the actual part.
I waited over 6mos for the eBay seller to get in some stock, until he told me to stop messaging, no more were going to be provided by Acer. Trying to get prices from the other two suppliers resulted in waiting for call-backs which never happened. I'm as furious as anybody else about this situation.
However, I seem to have given my R7-371T a little more life: I cautiously and slightly bent the pole on the inside of the female jack receptacle (i.e. the post inside the jack hole on the laptop). Now when the cable/male end is inserted, I think the slightly bent pole must get better/more consistent contact, and the power flip-flopping has stopped.
No doubt this will only last for a few months or a year, but IMO it's a win in this circumstance.
