I tried plugging something into my 19.  And it's like it doesn't fit well, the thing pops out right away.  Is there a special thing to stick in there that locks in place?

maybe a cigar lighter?

I haven't tried that but I'm not looking to light cigars

I know on my wife's matrix same thing happens with some devices, the outlet its self is to tight and the device end is tapered. 

not sure if its the same thing but just to let you know
most the time I can really shove it in but its a PIA to get out after.

 

I will zip tie the plug to the rubber cap.

 

It would be nice if someone would come out with a lockable setup that would stay connected.