Willow branches or part of a milo stalk have worked for me in a pinch. My common 870/Ithaca 37 plug is a cut off plastic clothes hanger. For a Beretta 391 I use a wire clothes hanger cut to correct length, small wooden dowel rod also works.
I've got the correct plugs, I just always forget which 'safe' place I put them up in the last time I used them.
