If all you can find are ones that fit 12.5mm you are looking at 2.5 inch (Laptop/SSD) drive sizes. You want to look up 3.5 inch hard drive Enclosures likehttp://www.newegg.com/Product/Product.aspx?Item=N82E16817182245
I like Rosewill. They are good and Cheap. I have a USB 2.0 enclosure that I have had for about 5 years not without issue.