My dad's 66 Valiant came with the square mirror seen in the picture below. The mirror is broken and will not stay up. When I went online to look to buy a replacement, the only options I saw available were round mirrors. Anyone have any advice on where I can find a replacement mirror like the one in the picture? Does the round mirrors that all of the vendors sell essentially mount the same as this one if we replace it? Appreciate some insight. Thanks.