Help mounting armrests please

[dbenamati]

I got two armrests out of a donor truck and want to mount them in my 67 which never had armrests (Basic metal skins). The mounting bracket in the door has two square holes which a clip or something fits into to screw into. I spent the afternoon at the local auto parts store looking for something that fills that hole like a clipped nut and nothing seems to work, also they have a lot of plastic parts but for this armrest, a metal part would be better. Could someone please look to see what fills the two square holes. I have nothing to compare to and the donor truck is gone. Thanks

Dave