They exist, it isn't a commonly ordered option, but I think I had it. I have 2 bolts drilled with blind nuts on my door, then I have 4 holes with no nuts for the current mirrors. I would like to be able to fill the 4 holes and bolt on using the blind nuts. It is a pain to have to pull the door panel off and reach around the window mechanisms just to remove the mirrors. And the current mirrors I have are no good.

Here is a link to a place that sells them, scroll down to see. I have found one other place, but prices are about the same. I also saw a set go for $25 on ebay a while back but I forgot to bid.

http://www.chevyduty.com/store/products.asp?dept=401