I have never bought clip on glasses on ebay, but I think there has to be some good clips provided. Whether you can buy the good one with a reasonable price depends on your comparing ability.
Before your final decision, make sure you have compared the prices, brands, sellers' reputation, and the comments given by former customers. You can buy a clip with good quality if you have done this.
No, I do not, but I heard somebody have the experience of buying that on ebay. As well all know, clip on sunglasses is just a simple thing but you will need a pair so that you need to go to find just the right size. On ebay, you can choose your right shapes, sizes and colors since there are a lot to choose from.